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So we're going to talk
a little bit about Bohr.

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00:00:18,751 --> 00:00:21,788
And then we're going to talk
about ionization energy, which

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is a theme that's going to
come back a couple more times.

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00:00:25,124 --> 00:00:27,627
Very important.

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00:00:27,627 --> 00:00:30,630
And then we're going quantum.

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00:00:30,630 --> 00:00:31,798
We're going quantum.

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And that's why this is a
very exciting day for me.

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And I'm hoping it
will be for you, too.

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It's why I have t-shirts.

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00:00:39,338 --> 00:00:40,439
It's also a goody bag day.

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There's just all sorts of
things happening today,

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so I'm very excited.

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This is how we ended our
lecture on Wednesday.

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I was showing you this as part
of my why this matters, which

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started with
refrigerators and then

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00:00:57,824 --> 00:01:00,893
we talked about a
chemistry problem, CFCs.

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And we talked about how
those were destroying

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the ozone layer of this planet.

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Now, why is that important?

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And I had this picture up
there to help explain it.

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Just to make sure
we all see what

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this is, I'm showing you here,
again, this is the energy--

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watts per meter squared--

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00:01:23,282 --> 00:01:25,852
that we get from the sun.

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And you can measure that up
on top of the atmosphere,

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so there is no atmosphere there.

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And this is what it looks like.

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That's the energy as a function
of the wavelength or frequency,

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or energy of the photon.

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00:01:39,398 --> 00:01:44,136
You now know how to go back
and forth between those.

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But see, on the planet here,
once you have the atmosphere,

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00:01:49,675 --> 00:01:50,943
you get a different spectrum.

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And the reason is--
and it's shown here--

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that some of the molecules
in the atmosphere

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are absorbing parts
of that spectrum.

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So what we see on the
planet is different.

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And we talked about this in
terms of why this matters

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and how ozone--

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00:02:06,259 --> 00:02:10,997
so I mentioned, oh, if we
can only see out here--

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the visible is here.

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00:02:12,231 --> 00:02:13,799
That's the visible.

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00:02:13,799 --> 00:02:15,434
There's the frequencies
of the visible.

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But what if it were here?

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The planet would
be totally dark,

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because no light would get
through the absorption that

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00:02:21,240 --> 00:02:24,343
happens from those molecules.

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00:02:24,343 --> 00:02:25,811
On the other hand,
over here, we've

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00:02:25,811 --> 00:02:28,714
got ozone that's protecting us.

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00:02:28,714 --> 00:02:33,819
It is absorbing light
in the higher frequency,

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00:02:33,819 --> 00:02:35,454
which means lower wavelength.

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00:02:35,454 --> 00:02:36,989
That's the UV.

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And that's why that was
such an important problem

53
00:02:38,991 --> 00:02:42,628
is to not destroy those
precious ozone molecules.

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So I wanted to make sure
that we-- and we understood

55
00:02:44,764 --> 00:02:46,933
this in terms of
energy transition,

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00:02:46,933 --> 00:02:49,268
because how do these
things absorb light?

57
00:02:49,268 --> 00:02:51,570
Well, they do just
what we said, which

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is they take the energy
from a kind of light

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00:02:54,740 --> 00:02:57,643
and an electron then
takes that energy,

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00:02:57,643 --> 00:03:01,047
absorbs it to be excited,
and it goes from one energy

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00:03:01,047 --> 00:03:02,915
level to another.

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00:03:02,915 --> 00:03:04,750
And we did that in terms
of the Bohr levels,

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so I wanted to do that.

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00:03:05,651 --> 00:03:08,688
And that is what
you have right here.

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00:03:08,688 --> 00:03:12,191
You have a way to see
that visible spectrum.

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So we'll talk
about that as well.

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00:03:14,760 --> 00:03:17,196
Let's talk about it right now,
because have a slide on it.

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So you have what is known as
a spectroscope, or the most

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00:03:22,868 --> 00:03:26,138
powerful way to see
light ever designed.

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00:03:26,138 --> 00:03:28,207
And if you look through this--

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OK, don't look at the UV please.

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Don't look at the sun.

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00:03:33,312 --> 00:03:34,513
Please don't do that.

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00:03:34,513 --> 00:03:37,583
But we gave you light
sources to look at.

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Like that, right?

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00:03:38,684 --> 00:03:39,785
Or you can look at that.

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00:03:39,785 --> 00:03:41,887
Or you can look at things
around you with it.

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00:03:41,887 --> 00:03:42,888
And what are you seeing?

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00:03:42,888 --> 00:03:44,323
You're seeing this.

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00:03:44,323 --> 00:03:46,892
You're seeing the
spectrum in the visible.

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00:03:46,892 --> 00:03:49,795
You're seeing it in this part.

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00:03:49,795 --> 00:03:51,831
But from this, you are also--

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00:03:51,831 --> 00:03:55,534
what you are seeing are
literally electron transitions.

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00:03:55,534 --> 00:03:57,069
You are literally
seeing-- and that's

85
00:03:57,069 --> 00:03:58,371
where I want you to think about.

86
00:03:58,371 --> 00:04:02,975
That's why I wanted you to have
this power, this power, which

87
00:04:02,975 --> 00:04:04,610
means responsibility,
as we know.

88
00:04:04,610 --> 00:04:06,712
But now, you can
not only see light.

89
00:04:06,712 --> 00:04:09,348
You can see electron
transitions.

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00:04:09,348 --> 00:04:13,719
I want you to think about
that as you're seeing light.

91
00:04:13,719 --> 00:04:16,988
And I want you to think about
it in terms of what we learned

92
00:04:16,988 --> 00:04:19,190
on Wednesday, which is Bohr.

93
00:04:19,190 --> 00:04:22,294
And so let's just put that here.

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So we had Bohr.

95
00:04:24,296 --> 00:04:30,836
And in the Bohr model,
we said the energy

96
00:04:30,836 --> 00:04:35,374
is going to be quantized
minus 13.6 electron volts

97
00:04:35,374 --> 00:04:41,480
times the atomic number
squared divided by n squared.

98
00:04:41,480 --> 00:04:45,851
And so for hydrogen,
for example, this

99
00:04:45,851 --> 00:04:52,324
is equal to minus 13.6 ev,
because e is 1 over n squared.

100
00:04:52,324 --> 00:04:57,963
So that was for
hydrogen. z equals 1.

101
00:04:57,963 --> 00:04:59,298
And so that's it.

102
00:04:59,298 --> 00:05:00,066
And that's it.

103
00:05:00,066 --> 00:05:04,970
n is equal to 1,
2, 3, et cetera.

104
00:05:04,970 --> 00:05:06,238
It's quantized.

105
00:05:06,238 --> 00:05:09,775
This was the whole kind
of discussion and theme

106
00:05:09,775 --> 00:05:11,877
of Wednesday's lecture.

107
00:05:11,877 --> 00:05:17,416
And that got us to these
levels, these Bohr levels,

108
00:05:17,416 --> 00:05:19,085
which are places where--

109
00:05:19,085 --> 00:05:23,355
energetic places,
energies of the electron.

110
00:05:23,355 --> 00:05:29,095
So we'd have these
levels that kept on going

111
00:05:29,095 --> 00:05:30,162
until you're at somehow--

112
00:05:32,731 --> 00:05:33,699
so this is energy.

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00:05:36,268 --> 00:05:40,172
And this would be like
n equals 1, n equals 2.

114
00:05:40,172 --> 00:05:41,907
These are the
energies right there.

115
00:05:41,907 --> 00:05:42,741
I'm just plugging in.

116
00:05:42,741 --> 00:05:44,909
And this would be
n equals infinity,

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00:05:44,909 --> 00:05:48,180
so the energy here would be 0.

118
00:05:48,180 --> 00:05:50,483
And for the hydrogen
atom, the energy

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00:05:50,483 --> 00:05:55,654
here would be minus
13.6 electron volts.

120
00:05:55,654 --> 00:05:57,123
That's hydrogen. So this is--

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00:05:57,123 --> 00:05:59,191
now, I'm leaving this here
and I want to use this.

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00:05:59,191 --> 00:06:01,494
That's why I'm
putting it back up.

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00:06:01,494 --> 00:06:03,295
Because look, now
you can use this

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00:06:03,295 --> 00:06:05,598
to start understanding light.

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00:06:05,598 --> 00:06:08,200
And so you use this, and
you look at light sources,

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00:06:08,200 --> 00:06:09,835
and you can start
thinking about things

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00:06:09,835 --> 00:06:11,203
in terms of energy transition.

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00:06:11,203 --> 00:06:12,037
So let's take a look.

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00:06:12,037 --> 00:06:16,142
So what if I just look at
some light sources, all right?

130
00:06:16,142 --> 00:06:17,877
OK, so that's what you see.

131
00:06:17,877 --> 00:06:19,478
That's the sun, all right?

132
00:06:19,478 --> 00:06:21,113
So that's daylight.

133
00:06:21,113 --> 00:06:24,049
And now we're getting into
the mode of seeing light

134
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like this, all right?

135
00:06:24,950 --> 00:06:29,221
It's an intensity, salute
versus wavelength, right?

136
00:06:29,221 --> 00:06:30,523
And there you go.

137
00:06:30,523 --> 00:06:33,425
And now if you look at sort
of an incandescent light bulb,

138
00:06:33,425 --> 00:06:34,793
it will look
something like this.

139
00:06:34,793 --> 00:06:36,595
So it's warm.

140
00:06:36,595 --> 00:06:38,164
There's a little
more red, all right?

141
00:06:38,164 --> 00:06:39,532
You can't get up to
the sun's temperature,

142
00:06:39,532 --> 00:06:40,766
but you can it pretty hot.

143
00:06:40,766 --> 00:06:43,435
So you see this nice
kind of looking spectrum.

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00:06:43,435 --> 00:06:45,771
And, oh, here's a
halogen. All right,

145
00:06:45,771 --> 00:06:47,806
that looks kind of closer maybe.

146
00:06:47,806 --> 00:06:52,978
Look at what happens
when we go fluorescent.

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00:06:52,978 --> 00:06:54,146
Look at that.

148
00:06:54,146 --> 00:06:57,616
Why does fluorescent
light give us headaches?

149
00:06:57,616 --> 00:06:59,451
Well, that might
be other reasons.

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00:06:59,451 --> 00:07:00,719
But look at this spectrum.

151
00:07:00,719 --> 00:07:02,254
That doesn't look like that.

152
00:07:02,254 --> 00:07:04,356
That's why we all have so
much trouble with fluor--

153
00:07:04,356 --> 00:07:05,791
and here's LEDs.

154
00:07:05,791 --> 00:07:08,727
And you can buy your cool white
LEDs and your warm white LEDs.

155
00:07:08,727 --> 00:07:10,996
But look, they're still not.

156
00:07:10,996 --> 00:07:12,298
They're not that, right?

157
00:07:12,298 --> 00:07:14,466
There's been a lot
of work on this.

158
00:07:14,466 --> 00:07:17,903
Can we get this to
be that, all right?

159
00:07:17,903 --> 00:07:24,910
And so now we are
armed with great power.

160
00:07:24,910 --> 00:07:26,579
And so you can look at things.

161
00:07:26,579 --> 00:07:29,114
You can say, oh,
I see that it has

162
00:07:29,114 --> 00:07:32,318
this large peak because I'm
looking at a fluorescent light

163
00:07:32,318 --> 00:07:32,851
within it.

164
00:07:32,851 --> 00:07:36,455
And I see that it's got this
stronger peak in the blue.

165
00:07:36,455 --> 00:07:38,490
Maybe I could just
absorb a little of that.

166
00:07:38,490 --> 00:07:40,492
What if I came up
with a coating,

167
00:07:40,492 --> 00:07:43,395
all right, that I could
put on that cool LED bulb

168
00:07:43,395 --> 00:07:46,565
to make it just a little
bit more look like that?

169
00:07:46,565 --> 00:07:48,601
Well, now we know
how to we might

170
00:07:48,601 --> 00:07:50,836
be able to use a board
to do this, all right?

171
00:07:50,836 --> 00:07:54,773
Because what if-- so let's
say, OK, the wavelength of that

172
00:07:54,773 --> 00:07:57,576
is around 450.

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00:07:57,576 --> 00:08:03,849
So if the wavelength is 450
nanometers, then I know--

174
00:08:03,849 --> 00:08:07,253
remember we did this--
waves, light waves,

175
00:08:07,253 --> 00:08:10,889
we can go back and forth
between frequency--

176
00:08:10,889 --> 00:08:11,590
hello.

177
00:08:11,590 --> 00:08:12,858
How's it going?

178
00:08:12,858 --> 00:08:15,494
All right, welcome to class.

179
00:08:15,494 --> 00:08:22,334
And energy, energy
equals hc over lambda.

180
00:08:22,334 --> 00:08:25,371
Oh, Planck, thank you.

181
00:08:25,371 --> 00:08:30,442
And this is roughly
2.75 electron volts

182
00:08:30,442 --> 00:08:34,980
for that wavelength 2.75
electron volts, right?

183
00:08:34,980 --> 00:08:37,182
OK, well, but see
now you say, but I

184
00:08:37,182 --> 00:08:40,719
want to absorb some
of those photons.

185
00:08:40,719 --> 00:08:41,986
I'll pose a problem.

186
00:08:41,986 --> 00:08:45,090
What if I have an atom--

187
00:08:45,090 --> 00:08:46,825
so question, right?

188
00:08:46,825 --> 00:08:55,367
So I have an atom,
an atom that has

189
00:08:55,367 --> 00:09:10,215
an n equal 4 to n equal 5
transition that absorbs.

190
00:09:10,215 --> 00:09:15,654
So I'm telling you
now this energy.

191
00:09:15,654 --> 00:09:18,657
So I'm telling you now
I've got some atom,

192
00:09:18,657 --> 00:09:22,127
and I know there's
a transition in it.

193
00:09:22,127 --> 00:09:24,396
It has an electron transition.

194
00:09:24,396 --> 00:09:27,132
Because remember, we're going
from electron transitions

195
00:09:27,132 --> 00:09:29,134
to light energy, back and
forth, back and forth.

196
00:09:29,134 --> 00:09:30,703
Look at this right here.

197
00:09:30,703 --> 00:09:32,504
I'm just saying, look,
OK, n equals-- just

198
00:09:32,504 --> 00:09:36,608
keep going. n equals 3,
n equals 4, n equals 5.

199
00:09:36,608 --> 00:09:38,243
So what I just asked
you is, I said.

200
00:09:38,243 --> 00:09:44,049
Well look, some atom has
a transition between n

201
00:09:44,049 --> 00:09:45,250
equals 4 and n equals 5.

202
00:09:45,250 --> 00:09:48,354
That means that if an
electron happens to be here,

203
00:09:48,354 --> 00:09:50,889
it can absorb energy
to promote it up

204
00:09:50,889 --> 00:09:54,993
to here of exactly 2.75 vb.

205
00:09:54,993 --> 00:09:57,629
Uh-huh, well, I can use Bohr.

206
00:09:57,629 --> 00:09:58,797
I can use Bohr now, right?

207
00:09:58,797 --> 00:10:01,166
Because so I can actually
answer this problem,

208
00:10:01,166 --> 00:10:02,334
answer this question.

209
00:10:02,334 --> 00:10:05,437
If I know that, then
I can say, well, OK,

210
00:10:05,437 --> 00:10:10,709
if the initial state is 4, and
the final state is 5, right--

211
00:10:10,709 --> 00:10:12,010
I've gone from 4 to 5.

212
00:10:12,010 --> 00:10:15,914
I've promoted an electron
up in energy, lifting it up

213
00:10:15,914 --> 00:10:20,819
like a ball against
gravity, all right?

214
00:10:20,819 --> 00:10:22,988
Then if then I can
use Bohr to say

215
00:10:22,988 --> 00:10:33,766
that 2.75 eV is equal to minus
13.6 z squared times 1 over 5

216
00:10:33,766 --> 00:10:37,302
squared minus 1
over 4 squared, that

217
00:10:37,302 --> 00:10:41,774
would be the transition
energy, this, dictated by Bohr.

218
00:10:41,774 --> 00:10:45,043
And, oh, I have
everything except z,

219
00:10:45,043 --> 00:10:46,478
which I can solve for.

220
00:10:46,478 --> 00:10:48,747
z equals 3.

221
00:10:48,747 --> 00:10:51,683
z equals 3, OK?

222
00:10:51,683 --> 00:10:54,052
So now all I need
to do is come up

223
00:10:54,052 --> 00:10:59,391
with a way to code all the
cool LEDs with lithium, right?

224
00:10:59,391 --> 00:11:00,392
Because this is lithium.

225
00:11:03,862 --> 00:11:06,765
And we'll be fine,
except there's a problem.

226
00:11:06,765 --> 00:11:08,667
And this is part of
the problem that we

227
00:11:08,667 --> 00:11:14,139
need to address and solve
today before the weekend.

228
00:11:14,139 --> 00:11:22,080
And that is that, see, Bohr
only works for one electron.

229
00:11:22,080 --> 00:11:24,416
Now, it's OK. z can be higher.

230
00:11:24,416 --> 00:11:25,884
z is 3, and it works here.

231
00:11:25,884 --> 00:11:30,889
But I assumed only one electron,
which means this really

232
00:11:30,889 --> 00:11:32,691
would be like li 2 plus.

233
00:11:32,691 --> 00:11:34,460
Oh, OK, we're going
to come back to that.

234
00:11:37,162 --> 00:11:48,707
But Bohr only for one
electron, all right?

235
00:11:48,707 --> 00:11:52,478
So if I'm going to get something
like z is 3, that's fine.

236
00:11:52,478 --> 00:11:54,480
But it can only have
one electron there.

237
00:11:54,480 --> 00:11:57,015
It can only have one
electron there or the model

238
00:11:57,015 --> 00:11:57,549
doesn't work.

239
00:11:57,549 --> 00:12:02,120
It was one electron with
some z of protons, all right?

240
00:12:02,120 --> 00:12:04,857
So this could be li 2 plus.

241
00:12:04,857 --> 00:12:09,862
That sounds harder to
put into a film, OK?

242
00:12:09,862 --> 00:12:12,197
We will be coming back to this.

243
00:12:12,197 --> 00:12:15,934
That is a serious limitation
of the Bohr model.

244
00:12:15,934 --> 00:12:20,138
And we can't do a lot if we can
only do one electron, right?

245
00:12:20,138 --> 00:12:25,310
You can do a lot of
ions, but that's it.

246
00:12:25,310 --> 00:12:29,147
OK, so I just said the word ion.

247
00:12:29,147 --> 00:12:35,854
What happens now if you take an
electron not from one level up

248
00:12:35,854 --> 00:12:38,223
in energy, but up, up,
up, up, up, all the way

249
00:12:38,223 --> 00:12:40,058
until it's free?

250
00:12:40,058 --> 00:12:41,627
What happens if you do that?

251
00:12:41,627 --> 00:12:44,162
Well, that is called ionization.

252
00:12:44,162 --> 00:12:46,532
That's ionization.

253
00:12:46,532 --> 00:12:50,002
And, in fact, when you look
out into the beautiful world,

254
00:12:50,002 --> 00:12:51,236
the universe--

255
00:12:51,236 --> 00:12:53,438
remember I said on
Wednesday, 75% of this

256
00:12:53,438 --> 00:12:56,241
is hydrogen. A whole
lot of it is ionized.

257
00:12:56,241 --> 00:13:00,612
It's getting ionized from energy
that's knocking electrons out.

258
00:13:00,612 --> 00:13:02,614
And then electrons
are coming back

259
00:13:02,614 --> 00:13:05,884
and cascading
through these levels,

260
00:13:05,884 --> 00:13:09,988
emitting discrete
frequencies of light.

261
00:13:09,988 --> 00:13:10,989
And this is what you see.

262
00:13:10,989 --> 00:13:12,357
It's beautiful, right?

263
00:13:12,357 --> 00:13:15,661
And what you're looking
at is ionized hydrogen

264
00:13:15,661 --> 00:13:18,730
getting electrons coming in
and cascading through the Bohr

265
00:13:18,730 --> 00:13:22,301
levels, all right?

266
00:13:22,301 --> 00:13:25,571
Ah, but what does ionized
hydrogen mean, right?

267
00:13:25,571 --> 00:13:28,407
OK, we can now understand it.

268
00:13:28,407 --> 00:13:30,108
We can now understand
it because now,

269
00:13:30,108 --> 00:13:32,744
instead of going
from 4 to 5, I'm

270
00:13:32,744 --> 00:13:35,380
going from anything to infinity.

271
00:13:35,380 --> 00:13:37,015
It's like escape
velocity, right?

272
00:13:37,015 --> 00:13:39,418
It's like, how much velocity
do I need to give something?

273
00:13:39,418 --> 00:13:43,021
So it just gets
away from the earth.

274
00:13:43,021 --> 00:13:45,958
And it's not going to feel the
earth's gravitational pull.

275
00:13:45,958 --> 00:13:47,926
Well, here, I don't
want this electron

276
00:13:47,926 --> 00:13:51,930
to feel the potential
of the atom anymore,

277
00:13:51,930 --> 00:13:54,132
the z, the positive charge.

278
00:13:54,132 --> 00:13:55,601
I want it to just be free.

279
00:13:55,601 --> 00:13:56,501
That's here.

280
00:13:56,501 --> 00:13:57,603
That's infinity.

281
00:13:57,603 --> 00:13:59,838
That's n equals
infinity, all right?

282
00:13:59,838 --> 00:14:04,509
So if I think about this,
that's actually quite easy

283
00:14:04,509 --> 00:14:11,216
to put into Bohr,
ionization energy.

284
00:14:11,216 --> 00:14:16,054
So to save time,
we'll write IE, right?

285
00:14:16,054 --> 00:14:20,892
And this is equal to the
energy required-- oh, I'm

286
00:14:20,892 --> 00:14:21,893
going to save time here.

287
00:14:21,893 --> 00:14:31,269
Look at that-- req'd to remove
the electron from the atom.

288
00:14:31,269 --> 00:14:33,438
OK, good.

289
00:14:33,438 --> 00:14:36,375
And if we think about
this in terms of Bohr,

290
00:14:36,375 --> 00:14:40,912
it would be minus 13.6--

291
00:14:40,912 --> 00:14:43,348
let's say for hydrogen, because
I've got hydrogen up there.

292
00:14:43,348 --> 00:14:46,351
So for hydrogen,
meaning z equals 1,

293
00:14:46,351 --> 00:14:50,188
it would be minus
13.6 times 1 squared--

294
00:14:50,188 --> 00:14:52,124
that's the z
squared, all right--

295
00:14:52,124 --> 00:15:00,198
times 1 over nf squared
minus 1 over ni squared.

296
00:15:00,198 --> 00:15:02,901
That's that delta
e, which equals

297
00:15:02,901 --> 00:15:10,942
minus 13.6 times 1 over
infinity minus 1 over ni

298
00:15:10,942 --> 00:15:13,945
squared, all right?

299
00:15:13,945 --> 00:15:15,747
And the last I checked
with my colleagues

300
00:15:15,747 --> 00:15:18,950
in the math
department, that's 0.

301
00:15:18,950 --> 00:15:20,752
That's 0, all right?

302
00:15:20,752 --> 00:15:23,321
So the ionization
energy, you literally

303
00:15:23,321 --> 00:15:24,589
can just read off here.

304
00:15:24,589 --> 00:15:27,392
If an electron is
in the ground state,

305
00:15:27,392 --> 00:15:30,962
if there's a happy electron
right here in this orbital,

306
00:15:30,962 --> 00:15:34,665
the amount of energy I need
to input into that atom

307
00:15:34,665 --> 00:15:38,036
to knock the electron fully
out, the ionization energy,

308
00:15:38,036 --> 00:15:40,405
is 13.6 electron volts, right?

309
00:15:40,405 --> 00:15:43,608
It's just the energy
of that orbital.

310
00:15:43,608 --> 00:15:48,046
I can get a little
fancier and say, well, OK,

311
00:15:48,046 --> 00:15:50,782
what about this question.

312
00:15:50,782 --> 00:15:54,886
What if I had light
with 100 nanometers?

313
00:15:54,886 --> 00:15:57,189
So now I'm telling you
my source, all right?

314
00:15:57,189 --> 00:15:58,256
Before I didn't tell you.

315
00:15:58,256 --> 00:16:00,258
Say something goes into
it and knocks it all out?

316
00:16:00,258 --> 00:16:02,160
No, now I know what's going in.

317
00:16:02,160 --> 00:16:09,434
The wavelength, or the energy of
the photons, is 100 nanometers.

318
00:16:09,434 --> 00:16:10,802
And I'm shining
that on hydrogen.

319
00:16:10,802 --> 00:16:13,338
Well, now, OK, let's see here.

320
00:16:13,338 --> 00:16:14,372
So a little example.

321
00:16:14,372 --> 00:16:15,841
Oh, I'm asking a question.

322
00:16:15,841 --> 00:16:17,476
What's the question?

323
00:16:17,476 --> 00:16:21,179
What is the lowest energy
level that the electron could

324
00:16:21,179 --> 00:16:25,383
be in such that a photon
from this light source

325
00:16:25,383 --> 00:16:26,918
ionizes the atom?

326
00:16:26,918 --> 00:16:30,655
OK, let's see, because
I now know the pieces,

327
00:16:30,655 --> 00:16:32,557
and I know the
definition, all right?

328
00:16:32,557 --> 00:16:39,831
So now if I have the energy
of 100 nanometer photon,

329
00:16:39,831 --> 00:16:40,665
well, that--

330
00:16:40,665 --> 00:16:43,001
I'm not going to go through it--

331
00:16:43,001 --> 00:16:46,204
is equal to 12.4 eV.

332
00:16:46,204 --> 00:16:46,938
Uh-huh.

333
00:16:46,938 --> 00:16:51,409
But see, if I now want to
use this to ionize hydrogen,

334
00:16:51,409 --> 00:16:53,011
then I get something like this.

335
00:16:53,011 --> 00:17:02,320
I get the delta E
equals minus 13.6 times

336
00:17:02,320 --> 00:17:05,857
1 oer infinity squared--

337
00:17:05,857 --> 00:17:07,592
OK, fine, we'll keep
that for a sec--

338
00:17:07,592 --> 00:17:10,862
minus 1 over ni squared, right?

339
00:17:10,862 --> 00:17:12,030
This is how much.

340
00:17:12,030 --> 00:17:15,400
This is how much
delta I need to ionize

341
00:17:15,400 --> 00:17:21,239
from any given place, any given
energy level ni, all right?

342
00:17:21,239 --> 00:17:21,973
OK?

343
00:17:21,973 --> 00:17:24,342
But I have 12.

344
00:17:24,342 --> 00:17:28,880
So what if I set this
equal to 12, all right?

345
00:17:28,880 --> 00:17:32,184
If I set this equal to
12.4, that's what I have.

346
00:17:32,184 --> 00:17:38,890
Then what I get
is ni equals 1.05.

347
00:17:38,890 --> 00:17:42,627
OK, good, that's my answer.

348
00:17:42,627 --> 00:17:43,895
No.

349
00:17:43,895 --> 00:17:45,197
Panic.

350
00:17:45,197 --> 00:17:46,898
Everybody should be panicking.

351
00:17:46,898 --> 00:17:48,200
No.

352
00:17:48,200 --> 00:17:50,202
That can't be my answer.

353
00:17:50,202 --> 00:17:52,103
I can't have--

354
00:17:52,103 --> 00:17:54,072
I can't have something
that's not an integer,

355
00:17:54,072 --> 00:17:56,942
because I said it over there
that n is a quantum number.

356
00:17:56,942 --> 00:18:00,579
1, 2, 3, nothing is
allowed in between.

357
00:18:00,579 --> 00:18:02,380
Mm-mm.

358
00:18:02,380 --> 00:18:06,918
So what you can see is
that I got so close.

359
00:18:06,918 --> 00:18:09,855
I almost had enough
energy to get n to be 1.

360
00:18:09,855 --> 00:18:10,956
But I don't.

361
00:18:10,956 --> 00:18:15,493
So I cannot use this light to
ionize an electron in n equals

362
00:18:15,493 --> 00:18:15,961
1.

363
00:18:15,961 --> 00:18:17,295
I can't.

364
00:18:17,295 --> 00:18:22,968
But I could use it to ionize an
electron in n equals 2, right?

365
00:18:22,968 --> 00:18:27,305
Because there, if n
is 2, well, then I've

366
00:18:27,305 --> 00:18:31,109
got actually plenty
of energy, all right?

367
00:18:31,109 --> 00:18:50,495
So cannot ionize from ni equals
1, but ni equals 2 is OK,

368
00:18:50,495 --> 00:18:50,962
all right?

369
00:18:50,962 --> 00:18:52,497
So that's the outcome of this.

370
00:18:52,497 --> 00:18:57,602
Now, I could also use that same
12.4 eV photon to ionize from n

371
00:18:57,602 --> 00:18:59,871
equals 3, or 4, or any of these.

372
00:18:59,871 --> 00:19:01,907
But I can't get to 1.

373
00:19:01,907 --> 00:19:03,909
And there's one other
concept that's important.

374
00:19:03,909 --> 00:19:08,446
Because look, I gave it 12.4 eV.

375
00:19:08,446 --> 00:19:11,082
What did I actually need?

376
00:19:11,082 --> 00:19:12,918
Well, you can even see it here.

377
00:19:12,918 --> 00:19:16,288
You know what these levels
are from the Bohr model.

378
00:19:16,288 --> 00:19:18,189
Here, this is 13.6.

379
00:19:18,189 --> 00:19:22,193
This is minus 3.4, OK?

380
00:19:22,193 --> 00:19:25,630
That's telling me this is
definitely not drawn to scale.

381
00:19:25,630 --> 00:19:30,201
But still, you get
the point, 3.4.

382
00:19:30,201 --> 00:19:33,171
And I just said, well, I could
probably get it out of 3.4.

383
00:19:33,171 --> 00:19:35,206
And I can because I've got 12.4.

384
00:19:35,206 --> 00:19:36,775
And so if I did this--

385
00:19:36,775 --> 00:19:42,213
so if ni equals 2, then I
would have excess energy.

386
00:19:42,213 --> 00:19:47,218
Excess energy would be
nine electron volts.

387
00:19:47,218 --> 00:19:49,020
And that is kinetic, right?

388
00:19:49,020 --> 00:19:53,124
So I've shot this thing
out of the atom with light

389
00:19:53,124 --> 00:19:55,794
that's got way more energy
than I needed to ionize it.

390
00:19:55,794 --> 00:19:59,130
But that energy, it's
still in the electron.

391
00:19:59,130 --> 00:20:03,134
I transferred that photon
energy to the electron energy.

392
00:20:03,134 --> 00:20:09,240
And so that is going to
be in the kinetic energy

393
00:20:09,240 --> 00:20:14,879
of the electron that's now
free, the electron free.

394
00:20:14,879 --> 00:20:19,451
I should have said
free electron, right?

395
00:20:19,451 --> 00:20:23,054
Excess kinetic energy comes
after ionizing, right?

396
00:20:23,054 --> 00:20:27,158
So these things are the
things we can do with Bohr.

397
00:20:27,158 --> 00:20:29,327
So I wanted to kind of take
what we learned Wednesday

398
00:20:29,327 --> 00:20:32,263
and apply it to a few
problems and go back and forth

399
00:20:32,263 --> 00:20:39,337
with this idea of photon
energy to Bohr level changes.

400
00:20:39,337 --> 00:20:42,107
And that's what I want you to
do in this week's goody bag

401
00:20:42,107 --> 00:20:43,441
as well.

402
00:20:43,441 --> 00:20:46,277
OK, now ionization is
an important concept.

403
00:20:46,277 --> 00:20:48,713
Like I said, we'll
be coming back to it.

404
00:20:48,713 --> 00:20:53,451
And you can actually plot--
and many people have measured,

405
00:20:53,451 --> 00:20:57,022
and this is very important-- the
ionization energy of elements,

406
00:20:57,022 --> 00:20:59,491
like as a function
of atomic number.

407
00:20:59,491 --> 00:21:04,362
And the first ionization
energy is important, right?

408
00:21:04,362 --> 00:21:05,997
The first line
ionization energy is

409
00:21:05,997 --> 00:21:10,769
the energy required to remove
the outermost electron, right?

410
00:21:10,769 --> 00:21:17,108
All right, so if I did have
a whole bunch of electrons,

411
00:21:17,108 --> 00:21:19,778
so if I had a whole
bunch of electrons.

412
00:21:19,778 --> 00:21:25,950
the first ionization, the
first ionization energy

413
00:21:25,950 --> 00:21:36,694
is the energy required to
remove the outermost one.

414
00:21:43,034 --> 00:21:44,702
So that's an important
number to know.

415
00:21:44,702 --> 00:21:47,439
If you want to take an
electron off of an atom--

416
00:21:47,439 --> 00:21:49,874
and will be doing
that because that's

417
00:21:49,874 --> 00:21:53,778
how we're going to make
our first bond next week--

418
00:21:53,778 --> 00:21:55,613
if you want to take an
electron off an atom,

419
00:21:55,613 --> 00:21:57,315
this is one of the
first things you ask.

420
00:21:57,315 --> 00:21:59,784
How much energy does
it take, all right?

421
00:21:59,784 --> 00:22:00,985
How much energy does it take?

422
00:22:00,985 --> 00:22:04,322
So that's an important concept
that we'll be coming back to.

423
00:22:04,322 --> 00:22:09,160
Now, OK, I alluded to the fact
that we needed a new theory.

424
00:22:09,160 --> 00:22:10,261
I already alluded to that.

425
00:22:10,261 --> 00:22:12,430
And I said that's where
we're going today.

426
00:22:12,430 --> 00:22:15,100
The Bohr model works for
one electron, as I said.

427
00:22:15,100 --> 00:22:17,735
All right, that means it's
good for hydrogen. Oh, we just

428
00:22:17,735 --> 00:22:20,171
ionized hydrogen, and
that was a lot of fun.

429
00:22:20,171 --> 00:22:27,912
And it's good for He plus, or
Li2 plus, or osmium 75 plus.

430
00:22:27,912 --> 00:22:30,482
Yeah, that's real.

431
00:22:30,482 --> 00:22:32,550
But what about two electrons?

432
00:22:32,550 --> 00:22:34,085
What about two, just two?

433
00:22:34,085 --> 00:22:35,920
Forget about 10, 20, 30.

434
00:22:35,920 --> 00:22:38,490
2, the Bohr model can't do it.

435
00:22:38,490 --> 00:22:39,724
It doesn't.

436
00:22:39,724 --> 00:22:42,127
It doesn't work for anything
more than one electron.

437
00:22:42,127 --> 00:22:44,562
It was derived for one electron,
and that's where it stays.

438
00:22:44,562 --> 00:22:46,030
So we're at this point now.

439
00:22:46,030 --> 00:22:48,766
This is the picture I started
to draw this week on Monday.

440
00:22:48,766 --> 00:22:51,603
And we're at a point where
we need something deeper.

441
00:22:51,603 --> 00:22:54,973
And some of the work that went
into this was really critical.

442
00:22:54,973 --> 00:22:57,575
And I'm not going to go
into too much detail,

443
00:22:57,575 --> 00:22:59,310
but there's one thing
I want you to know.

444
00:22:59,310 --> 00:23:03,114
So remember, Planck
and Einstein,

445
00:23:03,114 --> 00:23:05,483
they were playing with
quantization of light.

446
00:23:05,483 --> 00:23:08,219
And Einstein's photoelectric
effect found the particle

447
00:23:08,219 --> 00:23:12,223
nature of light, with Planck's--
you know, with together,

448
00:23:12,223 --> 00:23:18,429
their energy, equals h nu, that
quantized energy of the photon.

449
00:23:18,429 --> 00:23:20,965
And they saw it was a
particle, but it also

450
00:23:20,965 --> 00:23:23,268
was a wave, all right?

451
00:23:23,268 --> 00:23:26,437
There's a lot of
discussion, and interest,

452
00:23:26,437 --> 00:23:29,707
and attempt to
understand what it was.

453
00:23:29,707 --> 00:23:31,976
Was it a wave or a particle?

454
00:23:31,976 --> 00:23:33,878
And Compton did some
beautiful experiments

455
00:23:33,878 --> 00:23:35,980
to show, again,
evidence that it was

456
00:23:35,980 --> 00:23:39,884
a particle because
he saw how light

457
00:23:39,884 --> 00:23:41,085
interacted with electrons.

458
00:23:41,085 --> 00:23:45,657
And it was like this
collision that particles do.

459
00:23:45,657 --> 00:23:50,295
And then De Broglie,
or as [INAUDIBLE]..

460
00:23:50,295 --> 00:23:53,031
De Bro-- I don't know--

461
00:23:53,031 --> 00:23:56,201
would say he went further.

462
00:23:56,201 --> 00:23:58,269
De Broglie went further.

463
00:23:58,269 --> 00:24:00,838
He said, everything is both.

464
00:24:00,838 --> 00:24:03,374
Light, you guys don't know if
light is a particle or a wave.

465
00:24:03,374 --> 00:24:07,845
Well, I'm saying everything
is a wave, everything.

466
00:24:07,845 --> 00:24:10,014
And everything has this duality.

467
00:24:10,014 --> 00:24:12,050
So he wrote something
very important,

468
00:24:12,050 --> 00:24:17,021
which is the relationship
between anything's momentum

469
00:24:17,021 --> 00:24:17,755
and its wavelength.

470
00:24:17,755 --> 00:24:19,023
So we'll come back to this.

471
00:24:19,023 --> 00:24:20,191
So I want to write it down.

472
00:24:20,191 --> 00:24:28,132
So De Brog-- he said that
the wavelength of anything

473
00:24:28,132 --> 00:24:31,703
can be written as, oh,
that same quantization

474
00:24:31,703 --> 00:24:37,775
number, constant from Planck
divided by its momentum,

475
00:24:37,775 --> 00:24:39,677
literally, just its momentum.

476
00:24:39,677 --> 00:24:42,847
Anything has a wave
nature, anything.

477
00:24:42,847 --> 00:24:44,315
And light has a particle nature.

478
00:24:44,315 --> 00:24:45,683
What's going on?

479
00:24:45,683 --> 00:24:49,320
And it led Einstein
to say at the time--

480
00:24:49,320 --> 00:24:52,257
he said, quote, "It seems as
though we must use sometimes

481
00:24:52,257 --> 00:24:54,859
the one theory and sometimes
the other while at times

482
00:24:54,859 --> 00:24:56,327
we may use either.

483
00:24:56,327 --> 00:24:58,329
We are faced with a
new kind of difficulty.

484
00:24:58,329 --> 00:25:00,965
We have two contradictory
pictures of reality.

485
00:25:00,965 --> 00:25:02,600
Separately, neither
of them fully

486
00:25:02,600 --> 00:25:04,435
explains the phenomena of light.

487
00:25:04,435 --> 00:25:06,704
But together, they do.

488
00:25:06,704 --> 00:25:09,707
This was the beginning
of quantum mechanics.

489
00:25:09,707 --> 00:25:13,077
This is where they were.

490
00:25:13,077 --> 00:25:16,114
And later, once they really
got the quantum mechanics

491
00:25:16,114 --> 00:25:18,116
kind of going, he said this.

492
00:25:18,116 --> 00:25:19,717
The more success the
quantum mechanics

493
00:25:19,717 --> 00:25:21,886
has, the sillier it looks.

494
00:25:21,886 --> 00:25:23,121
Why?

495
00:25:23,121 --> 00:25:27,525
Well, there's only one way to
really learn about quantum,

496
00:25:27,525 --> 00:25:28,926
especially if it's
the first time.

497
00:25:28,926 --> 00:25:31,362
And that's from Dr.
Quantum himself.

498
00:25:31,362 --> 00:25:34,465
And so I do have a
video of Dr. Quantum.

499
00:25:34,465 --> 00:25:37,402
And I'm hoping you will
enjoy this with me.

500
00:25:37,402 --> 00:25:42,774
I enjoy it every time I
see it, most Friday nights.

501
00:25:42,774 --> 00:25:46,210
So let's watch Dr.
Quantum explain.

502
00:25:46,210 --> 00:25:52,116
Because there was one really
important experiment that

503
00:25:52,116 --> 00:25:54,385
happened that he's going
to explain right now

504
00:25:54,385 --> 00:25:55,787
called the double
slit experiment.

505
00:25:55,787 --> 00:25:57,655
And it changed everything.

506
00:25:57,655 --> 00:25:59,657
And I don't care if you
see it in another class.

507
00:25:59,657 --> 00:26:01,793
We're seeing it here
because this sets up

508
00:26:01,793 --> 00:26:04,762
what happens next in chemistry.

509
00:26:04,762 --> 00:26:06,064
Let's watch Dr. Quantum.

510
00:26:06,064 --> 00:26:07,065
--are.

511
00:26:07,065 --> 00:26:10,568
The granddaddy of all
quantum weirdness,

512
00:26:10,568 --> 00:26:13,504
the infamous double
slit experiment.

513
00:26:13,504 --> 00:26:16,140
To understand this
experiment, we first

514
00:26:16,140 --> 00:26:22,046
need to see how particles, or
little balls of matter act.

515
00:26:22,046 --> 00:26:24,816
If we randomly shoot
a small object,

516
00:26:24,816 --> 00:26:28,152
say a small marble
at the screen,

517
00:26:28,152 --> 00:26:30,355
we see a pattern
on the back wall

518
00:26:30,355 --> 00:26:33,691
where they went through
the slit and hit.

519
00:26:33,691 --> 00:26:37,328
Now, if we add a
second slit, we would

520
00:26:37,328 --> 00:26:41,165
expect to see a second band
duplicated to the right.

521
00:26:44,068 --> 00:26:47,605
Now, let's look at waves.

522
00:26:47,605 --> 00:26:51,342
The waves hit the
slit and radiate out,

523
00:26:51,342 --> 00:26:55,113
striking the back wall
with the most intensity

524
00:26:55,113 --> 00:26:58,549
directly in line with the slit.

525
00:26:58,549 --> 00:27:01,386
The line of brightness
on the back screen

526
00:27:01,386 --> 00:27:03,721
shows that intensity.

527
00:27:03,721 --> 00:27:07,091
This is similar to the
line the marbles make.

528
00:27:07,091 --> 00:27:14,632
But when we add the second slit,
something different happens.

529
00:27:14,632 --> 00:27:19,771
If the top of one wave meets
the bottom of another wave,

530
00:27:19,771 --> 00:27:22,507
they cancel each other out.

531
00:27:22,507 --> 00:27:27,211
So now there is an interference
pattern on the back wall.

532
00:27:27,211 --> 00:27:31,582
Places where the two tops meet
are the highest intensity,

533
00:27:31,582 --> 00:27:33,017
the bright lines.

534
00:27:33,017 --> 00:27:35,686
And where they cancel,
there is nothing.

535
00:27:35,686 --> 00:27:42,126
So when we throw things, that
is matter, through two slits,

536
00:27:42,126 --> 00:27:46,230
we get this, two bands of hits.

537
00:27:46,230 --> 00:27:49,600
And with waves, we get
an interference pattern

538
00:27:49,600 --> 00:27:52,236
of many bands.

539
00:27:52,236 --> 00:27:53,971
Good so far.

540
00:27:53,971 --> 00:27:56,607
Now, let's go quantum.

541
00:27:56,607 --> 00:27:57,708
It's my favorite line.

542
00:27:57,708 --> 00:28:01,245
I love that line.

543
00:28:01,245 --> 00:28:09,253
An electron is a tiny, tiny bit
of matter, like a tiny marble.

544
00:28:09,253 --> 00:28:12,690
Let's fire a stream
through one slit.

545
00:28:12,690 --> 00:28:17,795
It behaves just like the
marble, a single band.

546
00:28:17,795 --> 00:28:22,366
So if we shoot these tiny
bits through two slits,

547
00:28:22,366 --> 00:28:26,904
we should get, like
the marbles, two bands.

548
00:28:26,904 --> 00:28:28,639
What?

549
00:28:28,639 --> 00:28:31,108
An interference pattern.

550
00:28:31,108 --> 00:28:35,746
We fired electrons, tiny
bits of matter through.

551
00:28:35,746 --> 00:28:40,751
But we get a pattern like
waves, not like little marbles.

552
00:28:40,751 --> 00:28:42,186
How?

553
00:28:42,186 --> 00:28:45,823
How could pieces of matter
create an interference pattern

554
00:28:45,823 --> 00:28:47,658
like a wave?

555
00:28:47,658 --> 00:28:50,194
It doesn't make sense.

556
00:28:50,194 --> 00:28:52,597
But physicists are clever.

557
00:28:52,597 --> 00:28:55,333
They thought, maybe
those little balls

558
00:28:55,333 --> 00:28:59,136
are bouncing off each other
and creating that pattern.

559
00:28:59,136 --> 00:29:03,140
So they decide to shoot
electrons through one

560
00:29:03,140 --> 00:29:04,609
at a time.

561
00:29:04,609 --> 00:29:08,412
There is no way they could
interfere with each other.

562
00:29:08,412 --> 00:29:12,350
But after an hour of this,
the same interference pattern

563
00:29:12,350 --> 00:29:13,751
seemed to emerge.

564
00:29:13,751 --> 00:29:16,687
The conclusion is inescapable.

565
00:29:16,687 --> 00:29:19,790
The single electron
leaves as a particle,

566
00:29:19,790 --> 00:29:23,761
becomes a wave of potentials,
goes through both slits,

567
00:29:23,761 --> 00:29:28,699
and interferes with itself to
hit the wall like a particle.

568
00:29:28,699 --> 00:29:31,168
But mathematically,
it's even stranger.

569
00:29:31,168 --> 00:29:35,139
It goes through both slits,
and it goes through either,

570
00:29:35,139 --> 00:29:37,074
and it goes through
just once, and it

571
00:29:37,074 --> 00:29:38,242
goes through just the other.

572
00:29:38,242 --> 00:29:42,146
All of these possibilities
are in superposition

573
00:29:42,146 --> 00:29:43,247
with each other.

574
00:29:43,247 --> 00:29:45,983
But physicists were
completely baffled by this.

575
00:29:45,983 --> 00:29:49,020
So they decided to
peek and see which

576
00:29:49,020 --> 00:29:52,823
slit it actually goes through.

577
00:29:52,823 --> 00:29:55,726
They put a measuring
device by one slit

578
00:29:55,726 --> 00:30:01,265
to see which one it went
through, and let it fly.

579
00:30:01,265 --> 00:30:04,268
But the quantum world
is far more mysterious

580
00:30:04,268 --> 00:30:06,304
than they could have imagined.

581
00:30:06,304 --> 00:30:10,041
When they observed,
the electron went back

582
00:30:10,041 --> 00:30:12,109
to behaving like
a little marble.

583
00:30:12,109 --> 00:30:16,480
It produced a pattern of two
bans, not an interference

584
00:30:16,480 --> 00:30:18,549
pattern of many.

585
00:30:18,549 --> 00:30:23,754
The very act of
measuring, or observing

586
00:30:23,754 --> 00:30:26,657
which slit it went
through meant it only

587
00:30:26,657 --> 00:30:30,227
went through one, not both.

588
00:30:30,227 --> 00:30:36,067
The electron decided to act
differently as though it

589
00:30:36,067 --> 00:30:39,570
was aware it was being watched.

590
00:30:39,570 --> 00:30:44,075
And it was here that
physicists stepped forever

591
00:30:44,075 --> 00:30:48,512
into the strange neverworld
of quantum events.

592
00:30:48,512 --> 00:30:52,950
What is matter,
marbles or waves?

593
00:30:52,950 --> 00:30:55,252
And waves of what?

594
00:30:55,252 --> 00:31:00,524
And what does an observer
have to do with any of this?

595
00:31:00,524 --> 00:31:09,800
The observer collapsed the wave
function simply by observing.

596
00:31:09,800 --> 00:31:12,870
You can see why I show this.

597
00:31:12,870 --> 00:31:15,439
We do movie night at home a lot.

598
00:31:15,439 --> 00:31:16,707
It's Friday night, guys.

599
00:31:16,707 --> 00:31:22,647
Seriously, you know that you
might have a little free time.

600
00:31:22,647 --> 00:31:24,115
You get together
with some friends.

601
00:31:24,115 --> 00:31:25,449
There's no better way.

602
00:31:25,449 --> 00:31:28,919
But look, this is why--

603
00:31:28,919 --> 00:31:31,355
I hope that's as mindblowing
to you as it is to me.

604
00:31:31,355 --> 00:31:35,826
It was mindblowing
to them at the time.

605
00:31:35,826 --> 00:31:38,295
This led Bohr to
famously say, anyone

606
00:31:38,295 --> 00:31:42,667
who is not shocked by quantum
theory has not understood it.

607
00:31:42,667 --> 00:31:43,734
And here's the thing.

608
00:31:47,004 --> 00:31:51,375
There are some things in life
where you can ask questions,

609
00:31:51,375 --> 00:31:52,943
and you can understand them.

610
00:31:52,943 --> 00:31:54,912
You can answer them.

611
00:31:54,912 --> 00:31:57,748
I can ask the question
why do-- or somebody

612
00:31:57,748 --> 00:32:03,120
might say, why do I wear a
t-shirt under a sportcoat?

613
00:32:03,120 --> 00:32:06,657
That's weird, stylistically.

614
00:32:06,657 --> 00:32:08,492
I mean, stylistically, that's--

615
00:32:08,492 --> 00:32:10,394
and I say, well, OK,
here's the answer.

616
00:32:10,394 --> 00:32:13,497
Because I put comfort
over stylistic norms.

617
00:32:13,497 --> 00:32:15,766
Whatever, that's an answer.

618
00:32:15,766 --> 00:32:18,169
I could ask a harder question.

619
00:32:18,169 --> 00:32:20,337
I could ask a harder question.

620
00:32:20,337 --> 00:32:23,974
Why did Justin and
Selena break up?

621
00:32:23,974 --> 00:32:28,512
Because Jalina was totally
hashtag couple goals.

622
00:32:28,512 --> 00:32:29,246
Just saying.

623
00:32:29,246 --> 00:32:31,248
OK, anyway, now I'm just--

624
00:32:34,151 --> 00:32:35,086
why?

625
00:32:35,086 --> 00:32:38,189
Oh, but still that's
a harder question.

626
00:32:38,189 --> 00:32:39,890
Why?

627
00:32:39,890 --> 00:32:40,991
Because they were so good.

628
00:32:40,991 --> 00:32:45,062
But there's probably
an answer to that too.

629
00:32:45,062 --> 00:32:46,530
That's a harder question.

630
00:32:46,530 --> 00:32:48,799
This was mindblowing.

631
00:32:48,799 --> 00:32:51,535
How can something be both?

632
00:32:51,535 --> 00:32:53,738
How can something that
they know is a part of--

633
00:32:53,738 --> 00:32:57,341
How can everything be both?

634
00:32:57,341 --> 00:33:00,544
This was really
difficult to answer.

635
00:33:00,544 --> 00:33:04,181
And, in fact, the
real answer came

636
00:33:04,181 --> 00:33:08,919
with a mathematical solution,
which we'll learn next, but not

637
00:33:08,919 --> 00:33:09,987
quite understanding.

638
00:33:09,987 --> 00:33:13,090
We still don't really
understand quantum mechanics,

639
00:33:13,090 --> 00:33:14,291
even after 100 years.

640
00:33:14,291 --> 00:33:14,825
We don't.

641
00:33:17,394 --> 00:33:22,299
And so this is just, I think,
a beautiful part of our story,

642
00:33:22,299 --> 00:33:24,602
of our detective story.

643
00:33:24,602 --> 00:33:27,671
And just to show, people are
still working on this, right?

644
00:33:27,671 --> 00:33:30,674
How much quantum can we see?

645
00:33:30,674 --> 00:33:32,476
How much quantum can we see?

646
00:33:32,476 --> 00:33:37,148
Well, look, here's somebody
who, about 15 years ago--

647
00:33:37,148 --> 00:33:38,582
and it's published
in this paper--

648
00:33:38,582 --> 00:33:40,584
and a little more,
almost 20 now.

649
00:33:40,584 --> 00:33:42,419
They actually took--
forget about electrons.

650
00:33:42,419 --> 00:33:43,888
Those are teeny, tiny things.

651
00:33:43,888 --> 00:33:47,424
This is a whole group
of 60 carbon atoms.

652
00:33:47,424 --> 00:33:49,226
That's called the fullerene.

653
00:33:49,226 --> 00:33:51,328
And they shot this through--

654
00:33:51,328 --> 00:33:53,430
they did the double slit
experiment with this.

655
00:33:53,430 --> 00:33:55,332
And they showed that
with the grading--

656
00:33:55,332 --> 00:33:57,701
wait, without, you get the
signal peak, just like we saw.

657
00:33:57,701 --> 00:34:00,704
And with you get interference.

658
00:34:00,704 --> 00:34:02,339
You get interference.

659
00:34:02,339 --> 00:34:04,074
So they were able to
show all the way up

660
00:34:04,074 --> 00:34:07,511
to a large molecule,
60 carbon atoms,

661
00:34:07,511 --> 00:34:10,347
that these things are
still-- they have wavelength.

662
00:34:10,347 --> 00:34:13,449
They have these incredibly
strange properties

663
00:34:13,449 --> 00:34:16,053
that you just saw in the
double slit experiment.

664
00:34:16,053 --> 00:34:21,425
All, everything has this
duality, this duality

665
00:34:21,425 --> 00:34:25,629
between waves and particles.

666
00:34:25,629 --> 00:34:32,069
Now, OK, so we needed
a new model, right?

667
00:34:32,069 --> 00:34:34,371
Bohr can only do one electron.

668
00:34:34,371 --> 00:34:37,641
And meanwhile, there's all
this stuff going on at the time

669
00:34:37,641 --> 00:34:41,178
showing that you
need a new theory.

670
00:34:41,178 --> 00:34:43,647
How do we explain waves?

671
00:34:43,647 --> 00:34:46,116
And to kind of put
a little bit more

672
00:34:46,116 --> 00:34:51,121
of the nail in the coffin
for Bohr, you had Heisenberg.

673
00:34:51,121 --> 00:34:52,922
So I'm just going to
write this on the board

674
00:34:52,922 --> 00:34:54,391
before I go into
why this matters.

675
00:34:56,193 --> 00:35:17,314
And what Heisenberg said is
that you cannot measure both

676
00:35:17,314 --> 00:35:23,487
position and momentum exactly.

677
00:35:23,487 --> 00:35:25,689
You can't get them both, OK?

678
00:35:25,689 --> 00:35:28,525
And that's called the Heisenberg
uncertainty principle.

679
00:35:28,525 --> 00:35:30,694
But that was it, because--
look, you look at that

680
00:35:30,694 --> 00:35:32,696
and you say, well,
he-- saying this.

681
00:35:32,696 --> 00:35:34,865
But in Bohr, you got them both.

682
00:35:34,865 --> 00:35:36,433
You've got them both exactly.

683
00:35:36,433 --> 00:35:39,003
Remember, I put
energy down there.

684
00:35:39,003 --> 00:35:42,339
But we also put r on
Wednesday, exactly.

685
00:35:42,339 --> 00:35:44,074
Gesundheit.

686
00:35:44,074 --> 00:35:45,075
You can't get them both.

687
00:35:45,075 --> 00:35:46,644
And if you can't get
them both, that's

688
00:35:46,644 --> 00:35:48,245
another problem with
Bohr because Bohr

689
00:35:48,245 --> 00:35:50,014
says you can get
them exactly, right?

690
00:35:50,014 --> 00:35:52,182
So we had these pointers,
double slit experiment,

691
00:35:52,182 --> 00:35:54,618
Heisenberg's
theories, all right,

692
00:35:54,618 --> 00:35:56,253
saying we need something more.

693
00:35:56,253 --> 00:35:57,454
We need something more.

694
00:35:57,454 --> 00:35:59,356
And I'll get to that.

695
00:35:59,356 --> 00:36:00,724
I want to do my
why this matters.

696
00:36:00,724 --> 00:36:04,028
And then I'll get to the more
that came, which we'll then

697
00:36:04,028 --> 00:36:05,829
expand on Monday.

698
00:36:08,465 --> 00:36:10,668
Before I do that, let's
do why this matters.

699
00:36:10,668 --> 00:36:14,204
So why is the fact that
an electron is a wave,

700
00:36:14,204 --> 00:36:16,373
why is that so important?

701
00:36:16,373 --> 00:36:20,644
Well, first of all, because
it sets up this detective

702
00:36:20,644 --> 00:36:24,648
story of the electron set up
this new theory that's coming,

703
00:36:24,648 --> 00:36:26,583
quantum mechanics, right?

704
00:36:26,583 --> 00:36:29,753
But also, it immediately, just
like we started painting with

705
00:36:29,753 --> 00:36:33,057
them, right-- remember that was
one of my why this matters--

706
00:36:33,057 --> 00:36:36,026
we also realized that
we could see with them.

707
00:36:36,026 --> 00:36:38,796
We could see with electrons.

708
00:36:38,796 --> 00:36:41,398
Because if electrons
are waves, then

709
00:36:41,398 --> 00:36:44,335
I can shine them just
like I shine light

710
00:36:44,335 --> 00:36:46,971
and see what it shows me, right?

711
00:36:46,971 --> 00:36:49,873
It can illuminate matter.

712
00:36:49,873 --> 00:36:54,611
So if you look at the
frequency here of light,

713
00:36:54,611 --> 00:36:58,782
this is an electromagnetic
spectrum-- radio, microwave,

714
00:36:58,782 --> 00:37:01,885
infrared, visible, UV.

715
00:37:01,885 --> 00:37:04,221
Now, here's the thing.

716
00:37:04,221 --> 00:37:08,692
If you want to see
something, some feature size,

717
00:37:08,692 --> 00:37:12,429
you're limited by the
wavelength of the light.

718
00:37:12,429 --> 00:37:16,433
It can't be bigger than the
features you're looking at,

719
00:37:16,433 --> 00:37:18,702
roughlyish, OK?

720
00:37:18,702 --> 00:37:21,071
That's what you'll-- so if
you're trying to see something

721
00:37:21,071 --> 00:37:23,907
tiny, but the wavelength
of light is really big,

722
00:37:23,907 --> 00:37:24,742
you won't see it.

723
00:37:24,742 --> 00:37:28,645
So we need-- let's say
we want to see atoms.

724
00:37:28,645 --> 00:37:32,983
Let's say we want to see
atoms, or even more, nuclei.

725
00:37:32,983 --> 00:37:33,851
Look at how tiny.

726
00:37:33,851 --> 00:37:36,487
Those are 10 to the minus n,
10 to the minus 12 meters.

727
00:37:36,487 --> 00:37:38,288
Those are x-rays or gamma rays.

728
00:37:38,288 --> 00:37:41,258
But the problem is, if we
shine x-rays on things--

729
00:37:41,258 --> 00:37:45,095
and we will do that when
we look at crystals--

730
00:37:45,095 --> 00:37:46,663
but if we shine
x-rays, it's very hard

731
00:37:46,663 --> 00:37:49,466
to then collect them and
make a photographic image,

732
00:37:49,466 --> 00:37:53,270
OK, at least one that
gets you that resolution.

733
00:37:53,270 --> 00:37:57,674
And gamma rays are even
harder to catch, all right?

734
00:37:57,674 --> 00:37:59,376
But see, here's the thing.

735
00:37:59,376 --> 00:38:04,748
The electrons give you
exactly what you need.

736
00:38:04,748 --> 00:38:08,852
Because if we do this
math for an electron--

737
00:38:08,852 --> 00:38:11,288
so bring this one back down--

738
00:38:11,288 --> 00:38:13,223
if we do this math
for an electron,

739
00:38:13,223 --> 00:38:14,591
well, I'm going to use--

740
00:38:14,591 --> 00:38:16,860
oh, I thought I
had the middle one.

741
00:38:16,860 --> 00:38:20,397
So if I have an electron-- let's
suppose I have an electron that

742
00:38:20,397 --> 00:38:20,864
is--

743
00:38:24,068 --> 00:38:32,976
electron, I'm going to say I
accelerate it over 100 volts.

744
00:38:32,976 --> 00:38:34,511
I'm going to take
an electron, and I'm

745
00:38:34,511 --> 00:38:35,913
going to put it over 100 volts.

746
00:38:35,913 --> 00:38:38,348
I'm going to give it some
kinetic energy, right?

747
00:38:38,348 --> 00:38:43,921
So it's kinetic energy is then
going to equal 100 eV, right?

748
00:38:43,921 --> 00:38:48,058
OK, so now I've got an electron
moving with a kinetic energy

749
00:38:48,058 --> 00:38:48,625
that's 100 eV.

750
00:38:48,625 --> 00:38:50,360
Now you can convert
this to joules,

751
00:38:50,360 --> 00:38:55,432
and you can set this equal
to 1/2 mv squared, right,

752
00:38:55,432 --> 00:38:58,368
mass of the electron times
its velocity squared.

753
00:38:58,368 --> 00:39:04,374
And then once you have the
velocity, so you get the V.

754
00:39:04,374 --> 00:39:09,646
And then once you have that, you
get the momentum, the p, right?

755
00:39:09,646 --> 00:39:13,350
And then once you have that,
you get the wavelength, right?

756
00:39:13,350 --> 00:39:16,653
So I can go now from
something that's easy to do.

757
00:39:16,653 --> 00:39:21,225
100 volts is a lot, but in a
lab safe, not in your dorm.

758
00:39:21,225 --> 00:39:23,460
You could apply 100
volts to an electron,

759
00:39:23,460 --> 00:39:25,496
get it going at this speed.

760
00:39:25,496 --> 00:39:27,664
And once you know the speed,
you know the momentum.

761
00:39:27,664 --> 00:39:30,734
And if you know mv, then
you know it's wavelength.

762
00:39:30,734 --> 00:39:35,472
In that case from
this relationship,

763
00:39:35,472 --> 00:39:39,877
you would get that it's
about 0.12 nanometers.

764
00:39:39,877 --> 00:39:41,311
But look at this.

765
00:39:41,311 --> 00:39:44,481
The wavelength of a simply
accelerated electron

766
00:39:44,481 --> 00:39:46,750
is right where I need it.

767
00:39:46,750 --> 00:39:48,785
It's right where I need it.

768
00:39:48,785 --> 00:39:51,522
It's an Angstrom, right?

769
00:39:51,522 --> 00:39:56,059
So now, if I take advantage
of the wavelengths of the wave

770
00:39:56,059 --> 00:40:00,230
nature of electrons and I
shine them on materials,

771
00:40:00,230 --> 00:40:02,399
then I can see
materials that way.

772
00:40:02,399 --> 00:40:03,800
And I can see them
at that scale.

773
00:40:03,800 --> 00:40:07,271
And we do that all
the time, all the time

774
00:40:07,271 --> 00:40:11,909
in many, many different areas of
technology and research today.

775
00:40:11,909 --> 00:40:14,645
We use electrons to image.

776
00:40:14,645 --> 00:40:16,547
In fact, the best
images you can get

777
00:40:16,547 --> 00:40:19,149
are made with
electrons, all right?

778
00:40:19,149 --> 00:40:21,652
Here's an example
of using what's

779
00:40:21,652 --> 00:40:23,720
called a scanning electron
microscope, all right?

780
00:40:23,720 --> 00:40:27,724
So you see a butterfly, but you
want to really see a butterfly,

781
00:40:27,724 --> 00:40:29,993
or we can go even further.

782
00:40:29,993 --> 00:40:32,262
And instead of just
drawing pictures

783
00:40:32,262 --> 00:40:34,798
of this these beautiful
materials made of carbon--

784
00:40:34,798 --> 00:40:37,534
those are called nanotubes.

785
00:40:37,534 --> 00:40:38,535
This is called graphene.

786
00:40:38,535 --> 00:40:39,536
Gesundheit.

787
00:40:39,536 --> 00:40:44,575
It's a single sheet of carbon
atoms, one atom thick material.

788
00:40:44,575 --> 00:40:47,477
Notice with these
materials every single atom

789
00:40:47,477 --> 00:40:48,845
is a surface atom.

790
00:40:48,845 --> 00:40:50,647
That's pretty cool.

791
00:40:50,647 --> 00:40:52,749
They also have lots of
other cool properties.

792
00:40:52,749 --> 00:40:56,019
And I'll give you examples
throughout other lectures

793
00:40:56,019 --> 00:40:59,022
of how these kinds of
materials can be used.

794
00:40:59,022 --> 00:41:00,757
But for now, I'm talking
about seeing them.

795
00:41:00,757 --> 00:41:03,060
And this is what happens
when you actually

796
00:41:03,060 --> 00:41:04,328
look at them with an electron.

797
00:41:04,328 --> 00:41:05,295
That's a nanotube.

798
00:41:05,295 --> 00:41:08,298
And here is a
picture of graphene.

799
00:41:08,298 --> 00:41:10,701
The only reason we
can see graphene

800
00:41:10,701 --> 00:41:12,869
is because we have electrons.

801
00:41:12,869 --> 00:41:17,040
And we take advantage of the
wave nature of those electrons.

802
00:41:17,040 --> 00:41:18,208
Well, you say, well, OK.

803
00:41:18,208 --> 00:41:20,410
But why does that matter?

804
00:41:20,410 --> 00:41:23,714
Well, that matters
tremendously, because one

805
00:41:23,714 --> 00:41:29,152
of the first experiments that
really did what Feynman, what

806
00:41:29,152 --> 00:41:30,854
Richard Feynman wanted--

807
00:41:30,854 --> 00:41:34,091
Richard Feynman predicted
the field of nanotechnology

808
00:41:34,091 --> 00:41:35,259
50 years ago.

809
00:41:35,259 --> 00:41:36,793
He gave a famous
speech at Caltex

810
00:41:36,793 --> 00:41:39,263
called There's Plenty
of Room at the Bottom.

811
00:41:39,263 --> 00:41:41,965
He's also an amazing teacher,
and he taught actually

812
00:41:41,965 --> 00:41:43,066
the double slit experiment.

813
00:41:43,066 --> 00:41:47,104
I highly recommend you
Googling that lecture.

814
00:41:47,104 --> 00:41:50,607
And he said that someday,
you can put the atom

815
00:41:50,607 --> 00:41:53,076
where you want, all right?

816
00:41:53,076 --> 00:41:57,014
And the first time that was
done was in 1989 by IBM.

817
00:41:57,014 --> 00:41:58,282
They had 35 xenon atoms.

818
00:41:58,282 --> 00:41:59,249
They moved them around.

819
00:41:59,249 --> 00:42:01,652
But the point is, you couldn't
realize nanotechnology.

820
00:42:01,652 --> 00:42:04,821
You couldn't realize the
ability to actually move atoms

821
00:42:04,821 --> 00:42:08,292
if you can't see them, right?

822
00:42:08,292 --> 00:42:11,728
And this, the ability to
see what you were doing

823
00:42:11,728 --> 00:42:13,130
changed everything.

824
00:42:13,130 --> 00:42:14,031
It changed everything.

825
00:42:14,031 --> 00:42:16,099
And nature had been doing this.

826
00:42:16,099 --> 00:42:17,200
And I love these examples.

827
00:42:17,200 --> 00:42:20,203
So nature has been doing
nanotech for a long time,

828
00:42:20,203 --> 00:42:21,004
all right?

829
00:42:21,004 --> 00:42:23,040
So you have the inner
ear of the frog.

830
00:42:23,040 --> 00:42:25,742
It's a cantilever that is
sensitive to a few nanometers

831
00:42:25,742 --> 00:42:26,276
of movement.

832
00:42:26,276 --> 00:42:27,944
The frog can actually hear that.

833
00:42:27,944 --> 00:42:29,479
You've got features
in the ant's eye.

834
00:42:29,479 --> 00:42:31,148
I love the silk moth.

835
00:42:31,148 --> 00:42:36,653
The male silk moth has a single
molecule detection system

836
00:42:36,653 --> 00:42:39,956
onboard that can sense a
single molecule pheromone.

837
00:42:39,956 --> 00:42:44,561
It can detect a female silk moth
two miles away, two miles away.

838
00:42:44,561 --> 00:42:46,763
We have nothing like that.

839
00:42:46,763 --> 00:42:48,498
We have no
technologies like that.

840
00:42:48,498 --> 00:42:51,034
I can't even tell if
someone's in the next room.

841
00:42:51,034 --> 00:42:54,071
I have to look at my
phone or something.

842
00:42:54,071 --> 00:42:56,673
This is because of
nanotechnology, that kind

843
00:42:56,673 --> 00:42:58,775
of detection system, all right?

844
00:42:58,775 --> 00:43:02,145
But it was the ability to
see atoms and molecules

845
00:43:02,145 --> 00:43:05,415
with electrons that
kind of blew open

846
00:43:05,415 --> 00:43:07,351
this entire field, all right?

847
00:43:07,351 --> 00:43:08,785
And it's made it
so that we can now

848
00:43:08,785 --> 00:43:11,154
try at least to rival nature.

849
00:43:11,154 --> 00:43:12,255
Here is one example.

850
00:43:12,255 --> 00:43:14,825
You're not just seeing
graphene, but check this out.

851
00:43:14,825 --> 00:43:17,094
You're seeing a single
atom of graphene,

852
00:43:17,094 --> 00:43:19,262
and you're seeing what
happens under a certain kind

853
00:43:19,262 --> 00:43:20,997
of irradiation.

854
00:43:20,997 --> 00:43:22,966
And you're seeing this hole.

855
00:43:22,966 --> 00:43:24,267
And you're seeing the hole grow.

856
00:43:24,267 --> 00:43:26,603
And that's really
important, because something

857
00:43:26,603 --> 00:43:29,072
I care a lot about
are membranes, right?

858
00:43:29,072 --> 00:43:30,640
And another one of
these matters, I'll

859
00:43:30,640 --> 00:43:31,641
tell you about membranes.

860
00:43:31,641 --> 00:43:35,112
But here, I'm actually making
the thinnest possible membrane

861
00:43:35,112 --> 00:43:38,081
that you could make because
it's only one atom thick.

862
00:43:38,081 --> 00:43:39,816
And I'm controlling
how I make that.

863
00:43:39,816 --> 00:43:42,119
But I would never know what
my controls do if I couldn't

864
00:43:42,119 --> 00:43:45,389
see it in real time, all right?

865
00:43:45,389 --> 00:43:47,657
So this is my why this matters.

866
00:43:47,657 --> 00:43:50,494
It's seeing things
at this scale.

867
00:43:50,494 --> 00:43:53,230
OK, so back to-- so
there's Heisenberg, right?

868
00:43:53,230 --> 00:43:56,299
So in every moment, the electron
is only inaccurate position

869
00:43:56,299 --> 00:43:57,367
and an accurate velocity.

870
00:43:57,367 --> 00:44:02,305
This was, again, saying Bohr,
you got to think harder.

871
00:44:02,305 --> 00:44:04,674
And we had all of
these experiments

872
00:44:04,674 --> 00:44:10,680
showing the particle wave
duality of nature and of atoms.

873
00:44:10,680 --> 00:44:13,049
And so the question
then became--

874
00:44:13,049 --> 00:44:15,318
all these pointers from
all these different places,

875
00:44:15,318 --> 00:44:19,055
the question became,
how do we describe

876
00:44:19,055 --> 00:44:21,057
this wave nature of matter?

877
00:44:21,057 --> 00:44:23,760
How do we describe an
electron as a wave?

878
00:44:23,760 --> 00:44:25,762
And I like this,
because not only

879
00:44:25,762 --> 00:44:28,965
do I think if Schrodinger had
a swimming pool this is what he

880
00:44:28,965 --> 00:44:31,668
would do with it, but
also I thought maybe

881
00:44:31,668 --> 00:44:34,070
this would be cool for
an MIT kind of swim test

882
00:44:34,070 --> 00:44:35,906
thing in the future.

883
00:44:35,906 --> 00:44:38,341
Because you can
see what happens.

884
00:44:38,341 --> 00:44:41,077
This, I want to do
this experiment.

885
00:44:41,077 --> 00:44:42,345
But this looks really fun.

886
00:44:42,345 --> 00:44:44,080
They're making waves.

887
00:44:44,080 --> 00:44:46,616
They're literally
making waves, right?

888
00:44:46,616 --> 00:44:49,052
And so the question
now-- look at that.

889
00:44:49,052 --> 00:44:51,254
See, but the question is,
how do you describe it?

890
00:44:51,254 --> 00:44:52,889
Well, there are wave equations.

891
00:44:52,889 --> 00:44:55,425
There are wave
equations that we know

892
00:44:55,425 --> 00:44:59,463
about that relate the position
of a wave to it's time change

893
00:44:59,463 --> 00:45:02,365
in velocity, all right?

894
00:45:02,365 --> 00:45:05,535
And the thing is, this is it.

895
00:45:05,535 --> 00:45:10,373
This is how we need to
describe an electron.

896
00:45:10,373 --> 00:45:12,809
Now, think about
it for a second.

897
00:45:12,809 --> 00:45:16,112
An electron-- by
the way, it just

898
00:45:16,112 --> 00:45:18,548
occurred to me that you should
take this on that same day.

899
00:45:18,548 --> 00:45:21,751
Because if they don't
have real candles,

900
00:45:21,751 --> 00:45:25,489
and they only have these,
you should have this handy

901
00:45:25,489 --> 00:45:29,092
because you might need to pull
it out and see what kind of LED

902
00:45:29,092 --> 00:45:30,327
they gave you.

903
00:45:30,327 --> 00:45:32,095
What does it look like?

904
00:45:32,095 --> 00:45:35,665
Anyway, OK, that
was a side point.

905
00:45:35,665 --> 00:45:39,836
Bohr says electrons can
only be in certain places.

906
00:45:39,836 --> 00:45:41,738
Well, that's
mindblowing because--

907
00:45:41,738 --> 00:45:44,407
by the way, think about that.

908
00:45:44,407 --> 00:45:45,942
An electron can only
be here or here.

909
00:45:45,942 --> 00:45:48,044
Oh, and by the way, it can
transition between them,

910
00:45:48,044 --> 00:45:50,847
but it never be between them.

911
00:45:50,847 --> 00:45:52,949
Did anyone catch that?

912
00:45:52,949 --> 00:45:54,518
What's up with that?

913
00:45:54,518 --> 00:45:55,785
It can't be between them.

914
00:45:55,785 --> 00:45:57,320
I am telling you that.

915
00:45:57,320 --> 00:45:58,622
But it can transition.

916
00:45:58,622 --> 00:45:59,322
Where did it go?

917
00:46:02,058 --> 00:46:05,996
Oh, OK, that's a weekend
kind of exercise.

918
00:46:05,996 --> 00:46:10,333
And now we're saying they're
not even in one place.

919
00:46:10,333 --> 00:46:12,435
They're waves.

920
00:46:12,435 --> 00:46:13,370
They're like the water.

921
00:46:18,708 --> 00:46:21,278
That's cra-- that really was
at the time-- they thought

922
00:46:21,278 --> 00:46:23,446
how is this possible, right?

923
00:46:23,446 --> 00:46:24,781
But Schrodinger came along.

924
00:46:24,781 --> 00:46:28,251
And he said, I'm going to
write down the equation anyway.

925
00:46:28,251 --> 00:46:33,456
And that was the
big contribution,

926
00:46:33,456 --> 00:46:36,893
the really critical contribution
that Schrodinger did, is he

927
00:46:36,893 --> 00:46:41,264
said, I'm going to write
down kind of like a Newton's

928
00:46:41,264 --> 00:46:44,935
equation, like nf equals ma,
but for quantum mechanics

929
00:46:44,935 --> 00:46:47,571
and for waves, like electrons.

930
00:46:47,571 --> 00:46:48,838
And I'm going to describe them.

931
00:46:48,838 --> 00:46:52,475
So he developed the
equation that we

932
00:46:52,475 --> 00:46:56,012
saw, that on Monday we'll
solve, to describe the wave

933
00:46:56,012 --> 00:46:58,415
nature of quantum mechanics.

934
00:46:58,415 --> 00:47:01,117
And just to end--

935
00:47:01,117 --> 00:47:04,287
so on Monday we'll pick up
with Schrodinger's equation

936
00:47:04,287 --> 00:47:05,388
for the atom.

937
00:47:05,388 --> 00:47:09,926
The question is, what does
this all mean for chemistry?

938
00:47:09,926 --> 00:47:10,760
What does this mean?

939
00:47:14,064 --> 00:47:17,300
We're not-- I'm not
teaching you quantum.

940
00:47:17,300 --> 00:47:19,869
I'm not teaching you
quantum just so you

941
00:47:19,869 --> 00:47:21,304
know quantum in isolation.

942
00:47:21,304 --> 00:47:24,074
I'm telling you about
it because it completely

943
00:47:24,074 --> 00:47:27,043
revolutionized chemistry.

944
00:47:27,043 --> 00:47:30,981
And that is where we will
answer that question on Monday.

945
00:47:30,981 --> 00:47:32,415
Have a really good weekend.

946
00:47:32,415 --> 00:47:33,249
[SIDE CONVERSATIONS]