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How do LEDs work? · Daniel and Kelly’s Extraordinary Universe

0:08
Speaker 1: Hey, Daniel, I have a question about Noble prices. Well,
0:11
Speaker 1: you know they aren't awarded until much later this year
0:13
Speaker 1: or so, don't stay up late and wait by your phone. Really,
0:16
Speaker 1: they don't give one for podcasts. No, and they also
0:19
Speaker 1: don't give a banana prize. Well, my question is about
0:21
Speaker 1: the Physics Nobel Prize. Well, I'm not staying up late
0:24
Speaker 1: and waiting by the phone either. Well, my question is
0:26
Speaker 1: whether it's given to some discovery that is deep or
0:30
Speaker 1: a discovery that's useful to humanity. Why does it have
0:32
Speaker 1: to be one or the other. Isn't deep knowledge also useful?
0:36
Speaker 1: Have you found new trinos to be useful to humanity?
0:39
Speaker 1: Not yet? Actually, I'm still waiting for aliens to teach
0:42
Speaker 1: us how to use new trinos to get a safe tan. Yeah,
0:45
Speaker 1: don't wait by the phone for that. Sweden call me, Jupiter,
0:49
Speaker 1: call me? What does that even mean? If they're Aliens
0:52
Speaker 1: and Jupiter? I want the Jovia Noble Prize for Best
0:55
Speaker 1: Podcast Sidekick. You're not the sidekick. I'm what what I am?
1:14
Speaker 1: John make cartoon is and the creator of PhD comments
1:17
Speaker 1: I'm Daniel. I'm a particle physicist, and until a moment ago,
1:20
Speaker 1: I thought I was the sidekick on this podcast, and
1:23
Speaker 1: so welcome to our podcast, the award winning science and
1:26
Speaker 1: physics podcast called Daniel and Jorge Explained the Universe. Remind
1:30
Speaker 1: me which award we won. We won the award for
1:33
Speaker 1: having no awards yet, the award for best podcast that
1:37
Speaker 1: features only two sidekicks. We're sidekicking it here on our podcast.
1:42
Speaker 1: But yeah, it's our podcast about physics and science and
1:45
Speaker 1: astronomy and the universe and everything in between. Our podcast
1:48
Speaker 1: in which we share with you the gorgeous, amazing mysteries
1:52
Speaker 1: of the universe. We take you on a mental tour
1:54
Speaker 1: to all the crazy stuff that's out there, that's in here,
1:57
Speaker 1: the tiny stuff, the huge stuff, and we explain it
2:00
Speaker 1: all to you in a way that we hope also
2:02
Speaker 1: makes you chuckle, yeah, because you know, we hope to
2:04
Speaker 1: open up your mind to the amazing and incredible things
2:07
Speaker 1: that are happening right now and the far reaches of
2:09
Speaker 1: the universe and the far corners of the Solar System.
2:12
Speaker 1: But we also kind of want to open your eyes
2:14
Speaker 1: to see you all of the amazing signs that's happening
2:17
Speaker 1: all around you right now. Because one of the most
2:19
Speaker 1: amazing things about physics is that the same laws of
2:22
Speaker 1: physics operate on black holes and nebula and neutron stars
2:26
Speaker 1: and you and me and everything in our world. This
2:30
Speaker 1: is one of the most earth shattering revelations of physics
2:33
Speaker 1: in the last few hundred years, that the physics of
2:35
Speaker 1: the cosmos and the physics of the every day are
2:37
Speaker 1: the same physics, which means that we can discover the
2:40
Speaker 1: secrets of the universe just by doing experiments in our laboratory. Yeah,
2:44
Speaker 1: it's all the same being trapped in a black hole
2:46
Speaker 1: or being trapped in your apartment for an indefinite amount
2:50
Speaker 1: of time. It's all the same. You can do physics anywhere.
2:52
Speaker 1: They're crushing in different ways. But it also means that
2:55
Speaker 1: we can look around us and find amazing crazy stuff
2:59
Speaker 1: that reveals the grits of the universe. Like quantum mechanics
3:02
Speaker 1: was not discovered inside a black hole. It was found
3:05
Speaker 1: just by shooting photons that weird kinds of metal. And
3:07
Speaker 1: so today we'll be talking about an invention. Dad, I
3:10
Speaker 1: would argue maybe is one of the most commonplace or
3:13
Speaker 1: most prevalent technologies out there in human technology human kind. Right,
3:18
Speaker 1: are you talking about the wheel fire the hoverboard, and
3:22
Speaker 1: I was hoping for the hoverboard. Hasn't had that happened yet, Daniel, No,
3:26
Speaker 1: it is not. But I'm sure somebody accidentally ordered a
3:29
Speaker 1: hoverboard on Amazon and got something else. You know. Well,
3:31
Speaker 1: it's a technology that I think basically almost every human
3:35
Speaker 1: looks at on a daily basis, maybe even an hourly basis.
3:38
Speaker 1: Now you have me at the edge of my seat.
3:39
Speaker 1: What are we talking about today? What do you mean?
3:41
Speaker 1: I thought you knew what we were talking about today.
3:44
Speaker 1: I'm the sidekick here. Remember you're in charge. Oh I see,
3:47
Speaker 1: I see. Well, it's in our phones, you know, everyone
3:49
Speaker 1: looks at their phone every couple of minutes. It's on
3:51
Speaker 1: our computer screens and our televisions, which I'm sure a
3:53
Speaker 1: lot of people are watching a lot of these days.
3:55
Speaker 1: So it illuminates everything you're talking about. My sheer genius, right,
4:00
Speaker 1: my brilliance about Netflix. I'm just kidding. Well, it's I
4:04
Speaker 1: just figured out it's on the title of our podcast.
4:07
Speaker 1: So I'm guessing that people will already know by the
4:09
Speaker 1: time they click that's right. I hope they haven't been misled.
4:13
Speaker 1: That's right. We'll lead him to the light. That's right,
4:16
Speaker 1: So to have the podcast, we'll be talking about l
4:23
Speaker 1: E d S. How do elds work, what are the
4:25
Speaker 1: physics of it? And why did somebody win a Nobel
4:28
Speaker 1: Prize for inventing a particular color of it? That's right,
4:31
Speaker 1: We have physics Nobel Prizes for things like understanding quantum
4:35
Speaker 1: mechanics and figuring out what the basic particles are, or
4:39
Speaker 1: for you know, an observation of gravitational ways. Things really
4:42
Speaker 1: reveal the fundamental fabric and nature of the universe. And
4:46
Speaker 1: then we have Nobel Prizes for the invention of the
4:49
Speaker 1: blue led blue eled, not the red led. That one
4:52
Speaker 1: did not win. It was blued, Nobel's favorite color. Not
4:57
Speaker 1: at all, not at all. And so today we wanted
5:00
Speaker 1: to dive into, like what are the physics of L
5:02
Speaker 1: E d S. Is it's really worth a Nobel Prize?
5:05
Speaker 1: What are the sort of obstacles that they had to
5:07
Speaker 1: leap over in order to make this thing work? And
5:10
Speaker 1: what physics did they have to solve along the way.
5:12
Speaker 1: What does it reveal about the nature of our universe
5:15
Speaker 1: that we can now make L d's globe blues? So
5:17
Speaker 1: what do you think about my idea that it's maybe
5:19
Speaker 1: one of the most prevailing technologies out there, you mean
5:21
Speaker 1: lights in general, or LED specifically, L E D specifically,
5:25
Speaker 1: you know, because they're they're basically in every phone, and
5:27
Speaker 1: there's billions of phones out there, and it's on every
5:30
Speaker 1: computer screen now in TV screen, most of the TV
5:33
Speaker 1: screens have them. I would say it's up there along
5:35
Speaker 1: with a concrete and toilet paper as the current most
5:39
Speaker 1: important technology. Yeah. You know, people have been stockpiling L
5:42
Speaker 1: e d s ever since the coronavirus came out, you know,
5:44
Speaker 1: just in case, yeah, you know, just in case we
5:48
Speaker 1: run out of lights. I think you're right. Just had
5:49
Speaker 1: a really big impact on everyday life. You see them
5:52
Speaker 1: in screens, you see them in lights, you see them
5:54
Speaker 1: on trucks, you see them everywhere now. Yeah. Yeah, So
5:57
Speaker 1: it's a pretty important technology that's all around us, that
5:59
Speaker 1: is hitting our eyeballs all of the time. But as usually,
6:02
Speaker 1: we were wondering how many people out there know how
6:04
Speaker 1: L e d s work or what it even stands for.
6:07
Speaker 1: L E ED. So, as usual, Daniel went out into
6:09
Speaker 1: the world and ask people if they do how an
6:12
Speaker 1: LED works. That's right, and these questions actually pre date
6:15
Speaker 1: the coronavirus pandemic and so these are historical records of
6:20
Speaker 1: in person interviews back when that was still possible. Really, Oh,
6:24
Speaker 1: this is an actual on the street. These are from
6:26
Speaker 1: the archive. We haven't had a chance to pull this
6:28
Speaker 1: episode out yet. I see. Do you think people's opinions
6:31
Speaker 1: about l E d S would have changed by now?
6:33
Speaker 1: While people are spending more time inside under the life
6:37
Speaker 1: of a deeper relationship with L E d S. Now,
6:39
Speaker 1: maybe hypnotizes a little bit more since Yeah, well you know,
6:43
Speaker 1: people are looking at more screens and so they have
6:45
Speaker 1: hopefully more affection for L D. Yeah. So think about
6:47
Speaker 1: it for a second. If someone asked you how an
6:49
Speaker 1: LED works, would you know what to answer. Here's what
6:52
Speaker 1: people had to say. No, but I just know it's
6:54
Speaker 1: a better life. Part of me really wants you to
6:56
Speaker 1: say electricity, but uh, isn't it No, that's fluorescence. Remind
7:00
Speaker 1: I was gonna say gas, but let's just fluorescence light. Yeah,
7:06
Speaker 1: I'm going to assume it's due to a residents frequency
7:11
Speaker 1: within within the LED. I'm not sure. Essentially, it's just
7:17
Speaker 1: a PM junction. Um one side has holes in side
7:21
Speaker 1: has an accessible electrons, especially transitions in the state of
7:26
Speaker 1: the PM junction. Really slight. So yeah, oh shoot, um, honestly,
7:34
Speaker 1: I don't know. I literally don't know. Kind of yeah, yeah,
7:40
Speaker 1: I know, um excited Adams, but I forgot like which
7:46
Speaker 1: Adam like maybe alien They excited to higher state energy
7:51
Speaker 1: state and wave falls generated energy. But yeah, that's kind
7:58
Speaker 1: of isn't that. Florescen no similar, but fluorescence like much
8:04
Speaker 1: weaker energy. So what do you think of these responses?
8:06
Speaker 1: Pretty good? I feel like they fall in live with
8:09
Speaker 1: how I think about l d S, which is that
8:11
Speaker 1: I don't know much about him. Yeah, I was a
8:13
Speaker 1: little surprised. Some people had no idea. Some people thought
8:16
Speaker 1: they understood it, but we're actually talking about a completely
8:18
Speaker 1: different type of light generation that's fluorescence. People got them
8:22
Speaker 1: confused with fluorescent, Like yeah, yeah, In turns out there's
8:25
Speaker 1: lots of different ways to make light. You know, you
8:27
Speaker 1: incandescent light, we have fluorescent lights, and then we have
8:29
Speaker 1: led lights, and they all operate on really different physical principles. Yeah,
8:34
Speaker 1: because maybe maybe people have got them confused, because I
8:36
Speaker 1: feel like fluorescent lights, I know, they've been around for
8:39
Speaker 1: a long time, you know, like neon signs and things
8:41
Speaker 1: like that, and fluorescent bulbs, but they sort of made
8:44
Speaker 1: it into people's homes more recently, but then right away
8:47
Speaker 1: elid sort of came about and then totally replaced them. Yeah, well,
8:50
Speaker 1: fluorescent lights have been around for quite a long time,
8:53
Speaker 1: but yeah, they didn't make it into people's homes until
8:55
Speaker 1: recently with the compact fluorescence. But there's actually sort of
8:57
Speaker 1: a fascinating legal drama aout florescent lights because they were
9:02
Speaker 1: first developed pretty soon after incandescent lights, but then General
9:05
Speaker 1: Electric bought up all the patents and prevented anybody from
9:08
Speaker 1: developing them or using them, and basically kept fluorescent lights
9:12
Speaker 1: out of the market for decades just because they also
9:15
Speaker 1: owned the patents for incandescent lights. So it's sort of
9:18
Speaker 1: a legal political drama that we probably won't even get
9:20
Speaker 1: into today. They're like fluorescence that that works with gas,
9:23
Speaker 1: it's not electric. It's on brand with us, so we'll
9:25
Speaker 1: just sit in it. Yeah, they just sort of bought
9:27
Speaker 1: it up and sat on it as a dangerous technology
9:29
Speaker 1: that they thought would sort of endanger their business. Well,
9:32
Speaker 1: let's get into how LEDs work, but first let's maybe
9:36
Speaker 1: talk about how some of the other lights that people
9:38
Speaker 1: are familiar with work. So take us back, Daniel, how
9:41
Speaker 1: does it torch work. You know, that's a really awesome
9:44
Speaker 1: question actually, like what is fire and how does it work?
9:48
Speaker 1: And I want to do a whole podcast episode, Um,
9:50
Speaker 1: what is fire and what is the thing you're seeing
9:52
Speaker 1: that's glowing? And remember it's it's gonna be totally lit.
9:56
Speaker 1: M We're gonna brighten your life with that one. And
9:58
Speaker 1: remember on our live streams, somebody asked about that whether
10:01
Speaker 1: fire can have a shadow, which is a totally awesome question.
10:04
Speaker 1: But I think the first light that we should talk
10:06
Speaker 1: about is incandescent lights. And these are the ones that
10:09
Speaker 1: Edison invented, you know, the ones that people have had
10:11
Speaker 1: in their homes until very recently. It has a little
10:14
Speaker 1: filament in it that glows and eventually it breaks, right. Yeah,
10:18
Speaker 1: basically what people think of when they think of a
10:20
Speaker 1: light bulb, like a round thing with a little wire
10:22
Speaker 1: through the middle. Yeah, that's your classic light bulb. And
10:25
Speaker 1: all the technologies that we're gonna talk about today operate
10:28
Speaker 1: under the same essential goal, which is turned electricity into photons.
10:32
Speaker 1: Do you think when Edison had the idea for the
10:34
Speaker 1: light bulb, do you think he had a light bulb
10:36
Speaker 1: over his head? Like, was that the only time in
10:39
Speaker 1: history when like somebody was actually thinking of a light bulb,
10:42
Speaker 1: when they had an idea. Yeah, that's where it comes from, right,
10:44
Speaker 1: that was the first great idea, That was the first
10:46
Speaker 1: idea worthy of having a light bulb over your head. Technically,
10:51
Speaker 1: that's true. Yeah, And so the idea for incandescent lights
10:54
Speaker 1: is to find some material where you can deposit the
10:58
Speaker 1: energy from your electrons and it will give off light.
11:01
Speaker 1: All right, So every one of these strategies you want
11:03
Speaker 1: to turn fast moving electrons into shooting off photon photons
11:07
Speaker 1: to the surrounding areas. Okay, so how do incandescent lights work?
11:11
Speaker 1: How do light bulbs work? Regularly? The amazing thing about
11:14
Speaker 1: light bulbs that people probably don't understand is that they
11:16
Speaker 1: glow even when they're off. What. Yeah, everything glows. It's
11:21
Speaker 1: called black body radiation. Everything in the universe gives off photons,
11:25
Speaker 1: gives off radiation, even if it's totally black, even if
11:28
Speaker 1: it's a black hole, daddy. Well, technically, yes, black holes
11:32
Speaker 1: do give up a radiation all right, Yeah, that's true. Correct,
11:35
Speaker 1: Even black holes have a temperature. Right, Everything in the
11:37
Speaker 1: universe that's not an absolute zero glows at some spectrum. Now,
11:42
Speaker 1: usually you don't see it because it's invisible. It glows
11:45
Speaker 1: very very very long wavelengths, very low frequencies, and so
11:49
Speaker 1: you don't see it. So but this is why, for example,
11:52
Speaker 1: you know infrared telescopes like the James web Space telescope
11:56
Speaker 1: that looks for infrared light. It sees a lot out
12:00
Speaker 1: of noise that you don't even see and have to
12:02
Speaker 1: keep it cold a like negative fifty degrees or whatever.
12:05
Speaker 1: So everything in the universe is already glow, but it's
12:08
Speaker 1: not so useful, right, What you want is something that
12:10
Speaker 1: glows with light that you can see a lot. Right. Oh,
12:14
Speaker 1: I see black body radiation is in the infrared. It's
12:16
Speaker 1: much lower than the infrared. Yet most black body radiation,
12:19
Speaker 1: like the cosmic Marcrowave background radiation, is black body radiation
12:23
Speaker 1: from that initial plasma of the universe. And is it
12:26
Speaker 1: like you know, three degrees kelvin. It's a very very
12:29
Speaker 1: long wavelength. But what about something that's at zero degreek kelvin,
12:32
Speaker 1: like absolute zero? Would that still glow? You know, something
12:35
Speaker 1: that absolute zero can't glow. But there is nothing in
12:37
Speaker 1: the universe at absolute zero. So if you're like at
12:40
Speaker 1: point oh one degrees kelvin, from absolute zero, you would
12:45
Speaker 1: be glowing a little bit exactly. And that's why the
12:47
Speaker 1: black hole stuff is actually quite fascinating because when Stephen
12:50
Speaker 1: Hawking developed his ideas of black holes having a temperature,
12:54
Speaker 1: that automatically suggests that black holes should radiate, because like
12:58
Speaker 1: everything else that has a temperature, should radiat And that's
13:01
Speaker 1: why Hawkings results are sort of black hole thermo dynamics,
13:04
Speaker 1: because he's thinking about the temperature of black holes and
13:06
Speaker 1: how that connects to how they radiate. All right, so
13:08
Speaker 1: everything glows into infrared, So how do we get things
13:11
Speaker 1: to glow in the in the visible light the white
13:13
Speaker 1: light spectrum. Yes, so the spectrum in which you glow
13:15
Speaker 1: depends on your temperature. So really cold stuff glows in
13:19
Speaker 1: the infrared. If you heat something up, then its emissions
13:22
Speaker 1: move into the visible spectrum. So you want to make
13:25
Speaker 1: your filament glow in the visible light instead of in
13:27
Speaker 1: the infrared light. Than what you do is you make
13:29
Speaker 1: it hot, hotter and hotter. It turns the light from
13:32
Speaker 1: it not just glows more, but it changes color. It
13:35
Speaker 1: changes color. And that's why for example, you heat up
13:37
Speaker 1: metal right and you see it glows blue, it glows red,
13:40
Speaker 1: It glows white, for example, and the temperature of the
13:43
Speaker 1: metal determines the frequency at which it's glowing, right, Like
13:45
Speaker 1: white hot and red hot are different temperatures of metal R.
13:50
Speaker 1: And so this is a basic principle. And what's going
13:52
Speaker 1: on in the physics sense, like what's going on with
13:54
Speaker 1: the electrons on the atoms, why is it changing color?
13:56
Speaker 1: And how is it giving off the light. So it's
13:58
Speaker 1: always a good idea to try to think about stuff microscopically.
14:01
Speaker 1: And that's not just because I'm a particle physicist that
14:03
Speaker 1: I think we should always be thinking about the tiny stuff.
14:06
Speaker 1: I think it really does lead to some inside And
14:08
Speaker 1: so what's happening microscopically when you heat something up is
14:12
Speaker 1: that the electrons inside of the particles inside it have
14:15
Speaker 1: more ways to move. They're wiggling more, they're bouncing more.
14:18
Speaker 1: So there's just a lot more energy there. Now. The
14:21
Speaker 1: way something glows is when something moves from a higher
14:24
Speaker 1: energy level to a lower energy level. I mean, like
14:27
Speaker 1: the atoms in a decay or sort of degrade a
14:30
Speaker 1: little bit or chill out. And when they do that,
14:32
Speaker 1: they admit a hotel. Yeah, they're excited. They have some
14:34
Speaker 1: energy stored in them, and that energy comes from you know,
14:37
Speaker 1: whatever you did to heat up this material. Right, Heat
14:41
Speaker 1: means internal energy stored in the motion of these objects,
14:44
Speaker 1: and we had a whole podcast about what temperature means
14:46
Speaker 1: and it turns out to be very confusing and amazing,
14:49
Speaker 1: like everything else in the universe. But the way to
14:51
Speaker 1: think about microscopically is that these atoms are excited. Either
14:55
Speaker 1: the electrons that are whizzing around them have gone up
14:58
Speaker 1: one ladder in the energy level, or two ladders or
15:00
Speaker 1: three ladders, or maybe they're vibrating in new ways or
15:04
Speaker 1: rotating in new ways. These are all ways that they
15:06
Speaker 1: can store energy. The electrons are that are the atoms.
15:08
Speaker 1: The electrons can move up energy levels, but the atoms
15:11
Speaker 1: also they can vibrate. Remember a lot of these are
15:13
Speaker 1: in bonds, right. Metals are not just free floating gases.
15:16
Speaker 1: These lattices of things tied together and they're like you
15:20
Speaker 1: can imagine little springs between them, and then you can
15:22
Speaker 1: imagine those things vibrating and vibrating in different ways. They
15:25
Speaker 1: have different modes, all right. So they're excited and so
15:28
Speaker 1: they they're giving off energy and then they relax. Because
15:30
Speaker 1: things in the universe don't like to be excited. They
15:32
Speaker 1: like to spread out their energy, and that's why things
15:34
Speaker 1: emit energy because entropy, right, energy in the universe tends
15:38
Speaker 1: to diffuse, and so if you have it concentrated in
15:41
Speaker 1: one little mode, like one little electron has jumped up
15:43
Speaker 1: three energy levels, it will decay. You'll give that energy off.
15:47
Speaker 1: And the way it does that is by shooting off
15:49
Speaker 1: a photon. And so the more you heat up something up,
15:51
Speaker 1: the more you make all the atoms more excited, the
15:54
Speaker 1: more you know photons that are going to come off
15:56
Speaker 1: of this excitement exactly, and then the higher the energy
15:59
Speaker 1: of those gaps, So an electron can get pushed up
16:02
Speaker 1: several levels up that ladder, and then it can jump
16:04
Speaker 1: down five levels, and so then the photon has more energy,
16:08
Speaker 1: which corresponds to a higher frequency. So that's how, for example,
16:12
Speaker 1: hot objects can emit in the visible spectrum instead of
16:15
Speaker 1: just at the very very low energy levels. So the
16:18
Speaker 1: light that they emit has more energy, which is what
16:21
Speaker 1: higher frequency means, which is what visible light means, or
16:24
Speaker 1: invisible light has more energy per photon than infrared light.
16:29
Speaker 1: But I think it also has to be certain kinds
16:31
Speaker 1: of materials, right, like when I boil water, it doesn't
16:34
Speaker 1: start to blow. I mean it starts to glow in
16:36
Speaker 1: the infrared, but not in the visible light spectrum. That's
16:38
Speaker 1: an awesome question. How hot would you have to make
16:41
Speaker 1: water in order to make it glow? I don't think
16:43
Speaker 1: answer to that. That's a cool question. But you're right, Yeah,
16:45
Speaker 1: everything glows at some level, but not everything can be
16:48
Speaker 1: easily made to glow in the visible because I guess
16:50
Speaker 1: it will melt or burn or boil, yeah, exactly, something
16:54
Speaker 1: else will happened to it turn into vapor. And so
16:56
Speaker 1: that that's how light bulbs work. It's that they have
16:58
Speaker 1: a little thin wire of metal that you heat up
17:01
Speaker 1: and then that gives us the light. That's right. And
17:03
Speaker 1: the way you heat it up is that you send
17:05
Speaker 1: current through it, right, You send electricity through it. And
17:08
Speaker 1: most of these metals are resistors, meaning that they are
17:11
Speaker 1: not perfect conductors. So the electrons as they're trying to
17:14
Speaker 1: go through the metal are getting bounced into atoms, right,
17:17
Speaker 1: and those atoms are stealing their energy. And this is
17:21
Speaker 1: what heats up something when electricity passes through it. Like
17:24
Speaker 1: you know that block that you used to charge your laptop.
17:27
Speaker 1: Have you've been charging it for a while, it heats up, right,
17:29
Speaker 1: that's using. That's inefficient. It's using. It's stealing the electricity
17:34
Speaker 1: from those electrons in order to heat up that block.
17:37
Speaker 1: This is how you heat up the filament of tungsten.
17:39
Speaker 1: As you pass all this electricity through it, that heats
17:42
Speaker 1: it up and that makes it glow. Yeah, that's a
17:44
Speaker 1: little wire inside of the traditional light bulb and white tungsten.
17:48
Speaker 1: Is it a special kind of metal? They can heat
17:49
Speaker 1: up a lot without melting. Yeah, tungsten just sort of
17:52
Speaker 1: lasts a long time. But these things are really very
17:55
Speaker 1: very inefficient. Like it's not a very direct way to
17:58
Speaker 1: get energy into photons. Right, You're just heating this thing
18:01
Speaker 1: up and it's glowing somewhat in the visible but not
18:03
Speaker 1: always invisible, and a lot of the energy is just lost.
18:07
Speaker 1: A lot of the energy goes into the infrared, which
18:11
Speaker 1: is useless to us. Yeah, it just goes into making
18:13
Speaker 1: this thing hot, right, and not all the heat gets
18:16
Speaker 1: turned into visible light, and so only something like five
18:20
Speaker 1: of the energy that you put into a light bulb
18:22
Speaker 1: gets turned into light. Superficient, not super efficient and also
18:26
Speaker 1: kind of fragile, like you're baking this thing every single time,
18:30
Speaker 1: So it gets hot and then it gets cold, and
18:31
Speaker 1: gets hot and then it gets cold, and you know that,
18:34
Speaker 1: like that creates a lot of mechanical stress, which is
18:36
Speaker 1: why these filaments, which are already very very thin, don't
18:39
Speaker 1: last for that long. So your typical incandescent classic light
18:43
Speaker 1: bulb only works for about a thousand hours. Well, they're
18:46
Speaker 1: making a comeback, you know, and like hip her restaurants
18:48
Speaker 1: and stuff, everyone's going for the incandescent bulbs. Yeah. Well,
18:51
Speaker 1: the positive thing about incandescent bulbs is to have a
18:54
Speaker 1: very nice glow, Like it feels like sort of a
18:57
Speaker 1: natural light. You know that the process that produces this
19:00
Speaker 1: light gives you a spread, right, not just one color.
19:03
Speaker 1: It's not like a laser beam in your eye. It's
19:05
Speaker 1: a nice spread of warm white light. And so a
19:07
Speaker 1: lot of people like that. It's sort of more similar
19:09
Speaker 1: to sunlight than some of the other technologies we're gonna
19:12
Speaker 1: talk about, saying, all right, let's get into some of
19:13
Speaker 1: these other technologies like l d s, like fluorescent light bulbs,
19:18
Speaker 1: but first let's take a quick break. All right, there,
19:33
Speaker 1: we're talking about how LEDs work and specifically how lights
19:37
Speaker 1: work in general, and so we're going down the list
19:39
Speaker 1: of technologies, and so we talked about incandescent bulbs, which
19:42
Speaker 1: I'm guessing maybe my kids will never have to know
19:45
Speaker 1: how they work technically because everything is sort of moved on.
19:49
Speaker 1: But the next one in the history of light is
19:51
Speaker 1: the fluorescent light bulb. So you were saying these were
19:53
Speaker 1: invented out around the same time as the incandescent light bulb,
19:56
Speaker 1: but they worked on a totally different physics. Yeah, the
19:58
Speaker 1: physics is different. The idea here is to use excited gas,
20:02
Speaker 1: and you know, we talked about in the late eighteen
20:04
Speaker 1: hundreds of people were making vacuum tubes and you know,
20:07
Speaker 1: passing currents through it and seeing glows, and that's actually
20:10
Speaker 1: one of the things that lead to the discovery of
20:13
Speaker 1: the electron, right J. J. Thompson discovered the electron by
20:15
Speaker 1: playing with these sort of evacuated tubes and seeing how
20:18
Speaker 1: the gas inside them glows. But then people were playing
20:21
Speaker 1: with other kinds of things and discovered that if you
20:24
Speaker 1: pass a current through a tube that has gas in it,
20:27
Speaker 1: you can make the gas glow. And the physics here
20:30
Speaker 1: is pretty similar to the physics of incandescent lights, except
20:33
Speaker 1: that you're making a gas glow. Instead of making like
20:36
Speaker 1: a piece of metal glow, I see, instead of a
20:38
Speaker 1: little wire, it's like a tube of gas and you
20:41
Speaker 1: can excite the electrons in that gas. They go up
20:44
Speaker 1: an energy level and then they jump back down and
20:47
Speaker 1: they give off a photon. And I think last time
20:50
Speaker 1: we talked about these, it was it's sort of related
20:51
Speaker 1: to lightning the way kind of it's it's almost like
20:54
Speaker 1: you're creating a little bit of lightning in a bottle. Yeah,
20:56
Speaker 1: it's lightning in a bottle, and it's a little bit
20:58
Speaker 1: of plasma, right. You In order to pass electricity through
21:01
Speaker 1: a gas, you have to turn it into ions. You
21:03
Speaker 1: have to tear apart the positive and the negative that
21:06
Speaker 1: usually the gas is made out of and make an
21:09
Speaker 1: ion channel. And you know this sounds like Star Trek
21:11
Speaker 1: or whatever, but you're literally making a tube of electrically
21:16
Speaker 1: charged gas. It's like a gaseous wire sort of cool.
21:19
Speaker 1: It's like a gas that conducts electricity, right, and so
21:22
Speaker 1: you're tearing it apart just by creating this electric field
21:25
Speaker 1: from one side to the other and then passing that
21:28
Speaker 1: energy through and it excites the gas. It makes the
21:30
Speaker 1: gas like the atoms of the gas inside are now
21:34
Speaker 1: giving off there like absorbing these electrons that are going through,
21:37
Speaker 1: and then they give him off as photon. That's right.
21:39
Speaker 1: The microphysics of what's happening is that these electrons, the
21:41
Speaker 1: current that's passing through will sometimes bump into an electron
21:45
Speaker 1: in the gas atom and bump it up a few
21:48
Speaker 1: energy levels and then it will fall back down. And
21:50
Speaker 1: when it does that, it gives off a photon. So
21:53
Speaker 1: you're turning the kinetic energy of some initial electron into
21:56
Speaker 1: an excited state of the atomic electron, which then it's
22:00
Speaker 1: a photon. So that's how you get an energy from
22:02
Speaker 1: the electron into a photon. And it's kind of a
22:04
Speaker 1: binary process, right, Like it's hard to dim a fluorescent
22:08
Speaker 1: light bulb, right, Like a little regular ballb you can
22:11
Speaker 1: do that, but a fluorescent you know, it's either on
22:13
Speaker 1: and offer and if it's sort of on the edge,
22:15
Speaker 1: you'll blink and kind of give you ice cream. That's right.
22:17
Speaker 1: Because you need to create this plasma, you need to
22:19
Speaker 1: like ramp it up to a high enough voltage so
22:22
Speaker 1: that you can create this ion channel and the whole
22:24
Speaker 1: thing starts up. It's almost like starting up a little
22:27
Speaker 1: fusion reactor. Inside suddenly it Fluorescent light bulbs are way cool.
22:32
Speaker 1: They're lightning in a bottle and fusion bombs in a tube. Yeah,
22:35
Speaker 1: And the cool thing about them is that they're a
22:36
Speaker 1: lot more efficient doing this with gas. Like a mercury vapor,
22:40
Speaker 1: which is what's typically used, is something like twenty efficient
22:43
Speaker 1: instead of like the five percent of your incandescent light bulb.
22:47
Speaker 1: Where does the other scent efficiency go into heat as well?
22:51
Speaker 1: But they don't. They don't get as that that's exactly right.
22:53
Speaker 1: They don't get as hot, which is why they're more efficient. Right,
22:56
Speaker 1: some more the energy goes into creating light unless of
22:59
Speaker 1: it goes into like heating up the actual apparatus. So
23:02
Speaker 1: I think that all makes sense. One interesting facet which
23:05
Speaker 1: I thought was cool was that the best thing to
23:07
Speaker 1: use to make this light is mercury vapor because you
23:10
Speaker 1: don't need really high voltage and it's it's one of
23:13
Speaker 1: the most efficient ways to do it. But mercury is
23:15
Speaker 1: like super poisonous, which is which makes it like it's
23:19
Speaker 1: a bad idea. Also, mercury gives off light, it's not visible,
23:23
Speaker 1: it gives off ultra violet light. Oh my goodness, poisons
23:27
Speaker 1: you and gives you cancer at the same time. No,
23:30
Speaker 1: but that's why a lot of these fluorescent light bulbs
23:32
Speaker 1: are not clear. They're frosted because the inner side of
23:35
Speaker 1: the glass contains another material which absorbs the ultra violet light,
23:41
Speaker 1: uses some of the energy, and then gives off light
23:43
Speaker 1: in the visible So it's like a two step process.
23:45
Speaker 1: The mercury vapor gives off UV photons which are then
23:49
Speaker 1: like stepped down into the visible light by some phosphorescent
23:53
Speaker 1: coating inside the bowl. It's a lot to it. Yeah,
23:56
Speaker 1: it's a complicated thing, and you know, you have to
23:59
Speaker 1: create this plasma. And that's why florescent light bulbs until
24:01
Speaker 1: recently not as commonly used in the home. They're more
24:04
Speaker 1: expensive and more complicated, but there are a lot more
24:07
Speaker 1: efficient instead of five and they work for like ten
24:11
Speaker 1: thousand hours instead of a thousand hours. And the light
24:14
Speaker 1: is kind of different too. It's it's wider, generally, it's wider. Yeah,
24:18
Speaker 1: and it kind of drives me bonkers, Like I don't
24:20
Speaker 1: like the light from fluorescent light bulbs. It makes me
24:21
Speaker 1: feel like I'm you know, in a target or in
24:24
Speaker 1: like an alien autopsy examination room. Target and alien autopsy
24:30
Speaker 1: that's where your mind goes it's worse worst case scenarios. Well, actually,
24:34
Speaker 1: now that I think about it, I love to be
24:36
Speaker 1: in an alien autopsy or target for that, to be honest.
24:40
Speaker 1: It's just that I don't know why the lighting in
24:42
Speaker 1: alien autopsy scenes in science fiction is always so terrible,
24:46
Speaker 1: Like why do they always use the horrible fluorescent flickering lights?
24:50
Speaker 1: I see, Well, it's just so that the green comes
24:52
Speaker 1: out of their skin more, you know, makes this there's
24:55
Speaker 1: green skin seemed lovelier. I see. The aliens agent insisted
24:58
Speaker 1: that they have it that way, is in their contract. Alright, well,
25:02
Speaker 1: brown eminem's and fluorescent lights, that's right. And I didn't
25:11
Speaker 1: think that would make you laugh so much, Daniel. I
25:13
Speaker 1: don't think aliens are so vain alright, alright, well hopefully not.
25:17
Speaker 1: But yeah, so that's incandescent and fluorescent lights. And so
25:20
Speaker 1: let's get into the topic of the podcast, which is
25:22
Speaker 1: how LED lights work. And these are pretty pretty recent.
25:26
Speaker 1: I feel like in the last ten years they've become
25:28
Speaker 1: more popular, and they're also sort of everywhere right there,
25:32
Speaker 1: in phones, they're in TVs or pretty much every kind
25:34
Speaker 1: of screen, even on people's watches now have L E
25:37
Speaker 1: D s and so first of all, Daniel, what is
25:39
Speaker 1: l ED stand for. It stands for light emitting diode.
25:43
Speaker 1: Light emitting is obvious, right, giving off light and diode
25:47
Speaker 1: is this little physical thing that was invented in the
25:51
Speaker 1: fifties and sixties that's made out of semiconductors. And that's
25:54
Speaker 1: really the core idea here is that instead of using
25:57
Speaker 1: a hot little tube of metal or a hot tube
26:00
Speaker 1: of gas, let's see if we can build this thing
26:02
Speaker 1: out of semiconductors. And semiconductors are what computer chips are
26:06
Speaker 1: made out of, right, I mean, that's what computers are
26:09
Speaker 1: made out of. So this is kind of like they
26:11
Speaker 1: adapted that technology or they figured out they can also
26:14
Speaker 1: use it to midlight, they can also use to emdlight.
26:17
Speaker 1: And you're write, semiconductors are incredible also the basis of transistors,
26:21
Speaker 1: which is how we build computer chips. One of the
26:23
Speaker 1: cool things about semiconductors is that we can print them
26:26
Speaker 1: really Finally, we can construct super tiny circuits that have
26:29
Speaker 1: really specific semiconductors using lithography, and that's how we make
26:33
Speaker 1: computer chips so small, and we can make l ED
26:35
Speaker 1: s really small. But first maybe we should talk about
26:38
Speaker 1: like what a semiconductor is like, it's not somebody who's
26:41
Speaker 1: like driving a semi for example, someone who's dead driving
26:44
Speaker 1: with one eye closed, or conducting an orchestra, but only
26:48
Speaker 1: half the time, yeah, looking at their phone. And so
26:52
Speaker 1: to understand semiconductor you have to understand where it falls
26:54
Speaker 1: sort of between other objects like an insulator and a conductor.
26:57
Speaker 1: It's basically like a conductor that you can control right,
27:01
Speaker 1: like it's a resistor, but you can also shut it
27:04
Speaker 1: off if you give it a different sign sort of. Yeah,
27:06
Speaker 1: I think if it's sort of like a combination between
27:08
Speaker 1: an insulator and a conductor, because in an insulator, electrons
27:12
Speaker 1: cannot jump between atoms, like one atom has its electrons
27:15
Speaker 1: and the other one has its electrons, and electrons just
27:17
Speaker 1: stay in their atom. They have a little localized the
27:20
Speaker 1: neighborhood that they hang out in. But in a conductor,
27:23
Speaker 1: the electrons flow freely, like they don't necessarily have an assignment.
27:27
Speaker 1: They don't have like a home address. They just sort
27:28
Speaker 1: of like move around between atoms. It doesn't take much
27:31
Speaker 1: energy to go from one atom to the next. There's
27:34
Speaker 1: no barrier there. It insulates, you can't conduct electricity. Yeah,
27:38
Speaker 1: so insulators electrons can't jump between atoms, and a conductor,
27:41
Speaker 1: electrons just flow very easily between atoms. Now in the
27:44
Speaker 1: semiconductor has both, right, it has there's a flow zone
27:49
Speaker 1: and a no flow zone. So if you have enough energy,
27:51
Speaker 1: then you can get up into this conduction band where
27:54
Speaker 1: you can like float around between the atoms. So high
27:57
Speaker 1: energy electrons can jump between them, but low energy electrons
28:01
Speaker 1: are sort of stuck in their atom. So there's like
28:04
Speaker 1: the cool kids that are running all over the neighborhood
28:06
Speaker 1: and then the ones where their parents tell them they
28:08
Speaker 1: have to stay home. They're all mixed together. Yeah, and
28:09
Speaker 1: there's two different kinds and so based on how much
28:12
Speaker 1: energy you have, and so that's what we call this
28:14
Speaker 1: band gap. There's this energy gap. If you're above a
28:17
Speaker 1: certain energy that you can move around and below that
28:20
Speaker 1: you can't move around. And so that's what a semiconductor is.
28:22
Speaker 1: And it's fascinating because it has this band gap. And
28:25
Speaker 1: as you said, if you excite the electrons, you can
28:27
Speaker 1: turn into a conductor. And but some of the electrons
28:30
Speaker 1: they're low enough energy then they're an insulator. So you
28:33
Speaker 1: get this sort of fine grain control about the electrical flow,
28:36
Speaker 1: which is what makes it good for building circuits and
28:38
Speaker 1: all sorts of stuff. But it's it's not a question
28:40
Speaker 1: of the energy of the electrons, right, It's more of
28:43
Speaker 1: a question of the kind of the energy of the
28:45
Speaker 1: medium of the material. Yeah, the material determines sort of
28:48
Speaker 1: this structure, right. Different kinds of semiconductors have different size
28:52
Speaker 1: band gaps, but that band gap is the energy of
28:54
Speaker 1: the electrons that we're talking about. And you can build
28:57
Speaker 1: all sorts of different kinds of semiconductors. And you can
29:00
Speaker 1: build semiconductors based on like what material you use, like
29:04
Speaker 1: the gallium, is it, silicon, is it some combination of
29:06
Speaker 1: these two. You can build semiconductors that have a bunch
29:09
Speaker 1: of extra electrons in them, so that's called P type,
29:12
Speaker 1: like there's a bunch of extra electrons floating around. Or
29:15
Speaker 1: there's semiconductors that are called N types that have like
29:18
Speaker 1: empty holes where electrons should go. Yeah, so they're both semiconductors,
29:23
Speaker 1: and they're both about Usually mean add a silicon, right,
29:26
Speaker 1: with some sort of metal kind of infused in it. Yeah,
29:29
Speaker 1: And so you often start with silicon and then you
29:31
Speaker 1: add little bits of other stuff to make different kinds
29:34
Speaker 1: and a diode is just an N type semiconductor right
29:37
Speaker 1: next to a P type semiconductor. And what this means
29:40
Speaker 1: it's very simple. It just means the electricity can flow
29:42
Speaker 1: in one direction, and that's what a diode does. So
29:45
Speaker 1: the P type has a bunch of electrons and the
29:47
Speaker 1: N type has a bunch of holes for those electrons
29:49
Speaker 1: to fall into. So the P type one has electrons
29:52
Speaker 1: floating above this band gap that can move around, etcetera, cetera.
29:56
Speaker 1: When you put a current over, they just fall into
29:59
Speaker 1: the holes, and electrons jumping from high energy states to
30:03
Speaker 1: low energy states is how you emit energy. So when
30:07
Speaker 1: they do that, they release photons. So a diode is
30:10
Speaker 1: just P type and N type stuck together. And a
30:13
Speaker 1: light emitting diode is one where when the electrons fall
30:16
Speaker 1: in they emit visible light. And it has to be
30:19
Speaker 1: a special kind of material or is it still just
30:22
Speaker 1: silicon with some kind of metal in it. It has
30:24
Speaker 1: to be a special kind of material to get the
30:26
Speaker 1: right color light. And so that's really the key, that's
30:29
Speaker 1: the core physics for why blue L E d s
30:31
Speaker 1: were so fascinating. The first LEDs people invented, this gap
30:35
Speaker 1: was kind of small sort of hard to make it work.
30:37
Speaker 1: And so when they fell from P type to N type,
30:40
Speaker 1: they didn't have that much energy and they emitted mostly
30:42
Speaker 1: in the infrared. And that for example, the LED that's
30:46
Speaker 1: in your remote control, the when that controls your TV,
30:48
Speaker 1: you don't see light coming out of the top of
30:50
Speaker 1: the remote control because it comes out in a wavelength
30:53
Speaker 1: you can't see it comes out of infrared light to
30:55
Speaker 1: talk to your TV. But there's an infrared LED at
30:58
Speaker 1: the top of your remote control. And those are the
31:00
Speaker 1: first ones that are invented. Is actually back in the
31:02
Speaker 1: sixties that they first came out with infrared LEDs, and
31:06
Speaker 1: then the challenge was coming up with different kinds of
31:09
Speaker 1: material to negotiate this like P type N type difference.
31:13
Speaker 1: So you've got a larger gap so you have more
31:15
Speaker 1: energy when they fell, so you have more energy and
31:18
Speaker 1: the photons so they could be visible light. Uh So
31:21
Speaker 1: it's all about the difference between the P and the
31:23
Speaker 1: N types of materials. Okay, So it sort of depends
31:27
Speaker 1: more on the N type and the on the size
31:29
Speaker 1: of the hole. Now the hole is just a hole
31:30
Speaker 1: for an electron. It depends on the gap between the
31:33
Speaker 1: P type and the ND type. So you're right, it
31:35
Speaker 1: depends on the type of material and the size of
31:38
Speaker 1: this gap. And you're putting this P type of this
31:40
Speaker 1: N type next to each other, and it's basically how
31:42
Speaker 1: far they fall, Like, are they just stepping down from
31:44
Speaker 1: the curb and they go oop and they just give
31:46
Speaker 1: off a little bit of light or they jumping down
31:48
Speaker 1: Niagara falls and screaming all the way down and giving
31:51
Speaker 1: off a lot of energy. Oh, I see the electrons
31:53
Speaker 1: go from the P type to the N type. They jump, Yeah, yeah,
31:57
Speaker 1: they jump where they fall, you know, depending on whether
31:59
Speaker 1: you believe the electro is gonna make decisions. Man, they're
32:02
Speaker 1: pushed or pull more they're more like pulled, right, Yeah,
32:06
Speaker 1: they're more like pulled. And so basically an led is
32:08
Speaker 1: a bunch of electrons screaming. So make time you look
32:13
Speaker 1: at your phone. Your phone is screaming, screaming photons at
32:17
Speaker 1: you every time. Yeah, it's not just your brain that's
32:20
Speaker 1: screaming from your Twitter feed. And the thing that's amazing
32:22
Speaker 1: about this is that it's solid state, right, Nothing is
32:25
Speaker 1: moving here. You don't have gas that's bouncing around, you
32:28
Speaker 1: don't have metal that's heating up and cooling down. It's
32:31
Speaker 1: just fixed and it's just like electrical circuit, and that
32:33
Speaker 1: makes it last for a very very long time. It
32:36
Speaker 1: lasts for like a hundred thousand hours before it finally breaks.
32:40
Speaker 1: It like trust can scream for as long as you need.
32:43
Speaker 1: That's what you're saying. That's right. Unfortunately, the life span
32:47
Speaker 1: of electron it's very very long. It's doomed to a
32:50
Speaker 1: long life of falling down this gap. I guess my
32:52
Speaker 1: question is what keeps the light going? Like, once it
32:54
Speaker 1: falls into the hole, wouldn't it just stay in the hole? Yeah,
32:57
Speaker 1: it does, wouldn't it fill up all the holes? Well,
32:59
Speaker 1: you have a current it and so you're pulling these
33:01
Speaker 1: electrons out of the end type. So the whole thing
33:03
Speaker 1: is connected to a current. Imagine like a battery powering
33:05
Speaker 1: the led. It's sending fresh electrons into the p type
33:09
Speaker 1: and pulling the electrons out of the end type. So
33:12
Speaker 1: the whole thing is a circuit. It is like a waterfall.
33:14
Speaker 1: It's like a continual waterfall exactly. It's just like a waterfall.
33:17
Speaker 1: You're pumping on one side and then they scream on
33:19
Speaker 1: their way down. It's more like a roller coaster because
33:21
Speaker 1: of the screaming Yeah, that's right, because then they come
33:26
Speaker 1: back down and then the card gets pulled over and
33:29
Speaker 1: then up the rap again and then down and then screen.
33:31
Speaker 1: Let's not think of it as electron suffering, but electrons
33:34
Speaker 1: is having a lot of fun, that's right. And you know,
33:36
Speaker 1: you might wonder why do people go on roller coasters
33:38
Speaker 1: because they scream the whole time? Well, I guess they
33:40
Speaker 1: like to scream, and so we can imagine that also
33:43
Speaker 1: electrons are enjoying this ride. There's thrill seekers and they
33:48
Speaker 1: seem to be happy to do it because LEDs last
33:50
Speaker 1: for a hundred thousand hours and it's very very efficient.
33:54
Speaker 1: Most of the energy that you're sending into this circuit
33:56
Speaker 1: actually goes into emitting light. It's like more than fee
34:00
Speaker 1: percent of the energy. That's ten times, ten times more
34:03
Speaker 1: efficient than incandescent bulb. Yeah, ten times more efficient. And
34:07
Speaker 1: the challenge is in finding the right gaps you get
34:10
Speaker 1: the right energy level, so you get the right colors.
34:13
Speaker 1: And so the first thing was infra red, and then
34:16
Speaker 1: you know, infra red is the lowest frequency, the longest wavelength,
34:19
Speaker 1: and then they figured out ways to make them longer
34:21
Speaker 1: so they were visible and then longer, so you've got red,
34:24
Speaker 1: You've got green, and then the challenge was blue LEDs. Alright,
34:29
Speaker 1: let's get into the amazing discovery that was discovering blue
34:33
Speaker 1: LEDs and why I got the Nobel Prize. But first
34:36
Speaker 1: let's take a quick break. All right, Daniel, somebody got
34:52
Speaker 1: a Nobel Prize for discovering the blue led. So what's
34:56
Speaker 1: so special about blue led? I like the way you
34:58
Speaker 1: make it sound like they discovered a blue l D Like, well,
35:00
Speaker 1: I was sweeping up my lab and I found this
35:02
Speaker 1: thing on the ground. Oh my god, it's a blue LED. Right,
35:05
Speaker 1: It's just what I was looking for, because that's how
35:08
Speaker 1: we discover particles, right, you know, like, oh my gosh,
35:11
Speaker 1: look I found a towel particle, and now I get
35:12
Speaker 1: a Nobel Prize. I didn't like design it or engineer
35:16
Speaker 1: it or an invented, right, it should be more like
35:18
Speaker 1: it as somebody designed inventive. Yeah, somebody invented the blue led,
35:22
Speaker 1: which is sort of awesome and impressive. So we couldn't
35:25
Speaker 1: just take a white l ED and put a blue
35:27
Speaker 1: filter on it. Well, that's the thing. You can't make
35:29
Speaker 1: white l d s without blue. Right before we had
35:32
Speaker 1: blue l e d s, we had green, and we
35:34
Speaker 1: had read and so you couldn't make white l e
35:36
Speaker 1: d s. That's why blue l d s are so
35:38
Speaker 1: important because with blue you can make the combination you
35:42
Speaker 1: need to make white. And nobody wants in their reading
35:45
Speaker 1: light a green light or a red light. You want
35:48
Speaker 1: a white l e ED And you couldn't make white
35:50
Speaker 1: without blue. You need the blue. You need the blue
35:53
Speaker 1: to make the need the blue to make the white.
35:55
Speaker 1: And that's why l ds have exploded in applications everywhere
35:58
Speaker 1: because now they can make essentially any color because we
36:01
Speaker 1: have the missing blue cool. So tell me what was
36:04
Speaker 1: so hard about it and what's the physics behind it? Yeah,
36:06
Speaker 1: and so it's sort of an interesting question, like it
36:08
Speaker 1: really was an engineering puzzle, Like you just needed to
36:11
Speaker 1: get the right material. You needed to get the right
36:13
Speaker 1: material with the right thickness and configure it all correctly
36:16
Speaker 1: to get blue. And it was tricky to get this
36:19
Speaker 1: gap to be extra extra large, large enough to make
36:22
Speaker 1: so that when the electrons go down that roller coaster
36:24
Speaker 1: they scream for long enough to give you a blue photon.
36:28
Speaker 1: And you know, it turns out to be something of
36:29
Speaker 1: a condensed matter and solid state engineering problem and a
36:33
Speaker 1: couple of Japanese people figured it out. You need some
36:36
Speaker 1: mixture of gallium nitride with other silicon substrates and then
36:40
Speaker 1: you can get this blue led. But I guess why
36:42
Speaker 1: was it so hard? Like when you try to make
36:44
Speaker 1: electrons jump that much, it would burn out or they
36:47
Speaker 1: just wouldn't do it, or you know, they wouldn't scream
36:50
Speaker 1: as much as you wanted to. What was the difficulty
36:53
Speaker 1: in getting this right? It's just in finding one that
36:56
Speaker 1: would work. You know, most things just didn't have this
36:58
Speaker 1: large enough gap, and so it's just a finding a
37:00
Speaker 1: material that had this gap and that also worked. Yeah,
37:03
Speaker 1: and that also works. I mean, you can make a gap,
37:05
Speaker 1: but it may not necessarily work to get the electrons
37:07
Speaker 1: to flow across it, And so we can't necessarily predict
37:10
Speaker 1: in advance whether something is going to work. So they
37:12
Speaker 1: sort of had just had to search through lots of
37:14
Speaker 1: different kinds of materials and try this and try this,
37:16
Speaker 1: and have inside and inspiration and also just some luck
37:19
Speaker 1: into making it work. And so that's why I think
37:21
Speaker 1: it's interesting, like does this deserve a Physics Nobel Prize?
37:25
Speaker 1: Like there's no new principle discovered here, There's no fundamental
37:29
Speaker 1: revelation of the nature of the universe or space, time
37:33
Speaker 1: or history or whatever. It was an engineering step forward,
37:36
Speaker 1: which a deep respect for the engineering step forward. But
37:39
Speaker 1: I think the reason it got the Physics Nobel Prize
37:42
Speaker 1: is because of the huge impact on society. Really, you
37:46
Speaker 1: guys look down on things that are useful. You're like, well,
37:52
Speaker 1: you know, I think the original Nobel Prize was supposed
37:54
Speaker 1: to be about things that shape society, and so I
37:57
Speaker 1: think Alfred Nobel would probably be it. He pleased. But
38:01
Speaker 1: more recently a lot of these prizes have been awarded
38:04
Speaker 1: for like deep but maybe impractical discoveries about the nature
38:08
Speaker 1: of neutrinos or gravitational waves. I see, that's right. Nobel
38:12
Speaker 1: was an inventor, right, He wasn't a physicist, he was
38:15
Speaker 1: an engineering exactly. You guys have co opted our prize exactly.
38:19
Speaker 1: So in some sense this is like a return to
38:21
Speaker 1: Nobel's roots, right. It's recognizing something of great import to
38:25
Speaker 1: society because it has had a huge impact. It was
38:28
Speaker 1: like the missing piece. There's nothing weird physically about blue.
38:32
Speaker 1: It's just sort of the highest frequency and therefore the
38:34
Speaker 1: last for us to put together. I said, so do
38:37
Speaker 1: you think somebody should have gotten a prize, a Nobel
38:39
Speaker 1: prize for discovering the Higgs boson, because the people who
38:42
Speaker 1: wanted wanted for coming up sort of with the Higgs boson,
38:45
Speaker 1: but the people who discovered it, it was mostly just
38:47
Speaker 1: sort of engineering. Right. You just described my whole field
38:50
Speaker 1: as mostly sort of just engineering, which is so many
38:53
Speaker 1: it fastening the angles because I think you meant that
38:55
Speaker 1: as a disc but you described as engineering. So I
38:59
Speaker 1: hold engineering that at the highest esteem. That was actually
39:02
Speaker 1: trying to pay you a compliment. You were trying to
39:04
Speaker 1: elevate our field by describing ange. I appreciate that it's
39:07
Speaker 1: aspiring to be useful. Well, I'm not even sure how
39:10
Speaker 1: useful it is to discover the Higgs boson. But I
39:13
Speaker 1: think the great innovation there was definitely having the idea
39:17
Speaker 1: and finding it. I don't know how many big steps forward,
39:20
Speaker 1: and me it's a huge effort and technological achievement, But
39:23
Speaker 1: I don't know that we necessarily created anything new. We
39:27
Speaker 1: certainly didn't make anything as fascinating and impactful as the
39:30
Speaker 1: Blue Led. We just sort of confirmed an idea that
39:33
Speaker 1: it was in people's minds, so we revealed something about
39:36
Speaker 1: the nature of the universe, but something that sort of
39:38
Speaker 1: had been suspected to exist already. But okay, so back
39:42
Speaker 1: to the blue l d. That's important because now you
39:44
Speaker 1: have blue, and with red and green you can make
39:47
Speaker 1: white lights. So you can make any kind of color
39:49
Speaker 1: now that you have blue lads. Yes, exactly, And so
39:52
Speaker 1: these guys invented it in the nineties and then they
39:54
Speaker 1: won the No About Prize for it a few years later.
39:57
Speaker 1: That's how ladies work, and that's why there's important. So
40:00
Speaker 1: the people who discovered the red ladies and the green
40:02
Speaker 1: ladies also get a price, or only the one who
40:04
Speaker 1: waited till the end and procrastinated to discover the missing
40:09
Speaker 1: color get the prize. I feel like you have another
40:12
Speaker 1: horse in this race here, your pro procrastination. I built
40:16
Speaker 1: a whole career on it. Any Yeah, the lesson here
40:19
Speaker 1: is weight and just sort of put the period at
40:21
Speaker 1: the end of the sentence and you'll get the prize
40:23
Speaker 1: for everybody else's work. Yeah, there you go. But in
40:26
Speaker 1: a way, it's true, right, like the person who discovered
40:28
Speaker 1: the red and the green one didn't get a prize,
40:30
Speaker 1: but somehow, like you know, completing the triangle to get
40:33
Speaker 1: white light made a bigger splash. The person who puts
40:35
Speaker 1: the capstone on the top of the pyramid, right, is
40:38
Speaker 1: the one that claims the prize, right, the one who
40:40
Speaker 1: discovers the mass particles the one who But yeah, so
40:43
Speaker 1: now we can make white light with LEDs that is
40:45
Speaker 1: super efficient and also small, really small. Like maybe before
40:50
Speaker 1: you couldn't make incandescent bulbs small enough for you know,
40:54
Speaker 1: written and display kinds of screens, but now you can't
40:57
Speaker 1: because you can can really really small yeah, because we
41:00
Speaker 1: can print stomic conductor is using these lithography techniques to
41:03
Speaker 1: be really really super tiny. And you know, we invented
41:06
Speaker 1: these techniques mostly so we can make transistors really really small,
41:10
Speaker 1: so we can make computer chips packed with all sorts
41:13
Speaker 1: of little circuits on them. But we can also use
41:14
Speaker 1: the same technology to make l E d s and LEDs. Remember,
41:17
Speaker 1: are not monochromatic. They're not like tiny little lasers. Right,
41:21
Speaker 1: Lasers shoot exactly one frequency, are very very tight band
41:25
Speaker 1: and frequency because the photons come from one atomic step.
41:29
Speaker 1: Ellis are not quite like that. The light they admit
41:31
Speaker 1: is narrowly focused, doesn't have just a single wave length
41:35
Speaker 1: or frequency. It's like it is a little bit like
41:37
Speaker 1: in Contestant, and that it's kind of broad. Yeah. Yeah,
41:40
Speaker 1: they're broader than lasers, but not as broad as in Contestant.
41:43
Speaker 1: So that's why there are specific color, but they're not
41:45
Speaker 1: like a really tight band like lasers. So then when
41:48
Speaker 1: I turn on the flashlight on my phone and I
41:51
Speaker 1: see this wide light come off, and that helps me
41:53
Speaker 1: at night and get around at night, I'm actually seeing
41:56
Speaker 1: not a white led, but like a whole bunch of red,
41:59
Speaker 1: blue and green lads mixed together. That's right. And when
42:01
Speaker 1: you look on your screen and you see white for
42:04
Speaker 1: the blank page and the word document of the novel
42:06
Speaker 1: you've been writing for ten years, than what you're really
42:09
Speaker 1: seeing our red, green and blue blinking, your failure action blinking.
42:14
Speaker 1: But you know, that's what Newton discovered is that white
42:15
Speaker 1: light is actually just a mixture of colored lights. There's
42:18
Speaker 1: no difference, There is no white photon, there's no color
42:21
Speaker 1: in the spectrum that is white. White light is just
42:24
Speaker 1: a mixture of red, green, and blue. And so basically
42:27
Speaker 1: that increased our human level global efficiency for light by
42:33
Speaker 1: ten times. So now we can be a whole lot
42:36
Speaker 1: more eco friendly. Yeah, except probably just means we made
42:38
Speaker 1: a lot more bulbs, so probably using the same amount
42:40
Speaker 1: of electricity, and now we're just lighting everything up. You know,
42:44
Speaker 1: I changed all the light bulbs in my house for
42:46
Speaker 1: l d s and boy, your power bill drops like crazy. Yeah. Well,
42:50
Speaker 1: do you appreciate it though? For working? Like when you're
42:52
Speaker 1: drawing something, do you like using natural light or incandescent
42:56
Speaker 1: light or LED light or does it not make any
42:58
Speaker 1: difference because you do everything at well, I drive everything
43:02
Speaker 1: on the computer, so it's all LED power, baby, you know, yeah,
43:07
Speaker 1: I guess so. All right, Well that's pretty cool. I
43:10
Speaker 1: have a new respect for blue lads now, and also
43:13
Speaker 1: liver respy for red and green lads. You know, I
43:15
Speaker 1: feel like they got the short end of the colored triangle.
43:18
Speaker 1: They are singing the Nobel Blues, all right, but I think,
43:20
Speaker 1: you know, it points us to how even a small
43:23
Speaker 1: discovery in physics or experimental physics can lead to basically
43:27
Speaker 1: revolution and how we lead our lives and what kinds
43:30
Speaker 1: of devices we use every day. That's right. Engineering can
43:33
Speaker 1: change to the world. What can you guys replay that?
43:37
Speaker 1: Which is one more time? I just want to make
43:39
Speaker 1: sure that we heard it right. Can you replay it?
43:41
Speaker 1: Engineering can change to the world. You know, I'm gonna
43:46
Speaker 1: download it, frame it, frame it on an led frame.
43:49
Speaker 1: I should send you a little button. You can just
43:51
Speaker 1: press that and hear me say that. Hag into your
43:54
Speaker 1: phone and make it your ring tone. All right. Well,
43:59
Speaker 1: we hope you joined that, and we hope you look
44:01
Speaker 1: at light in a whole different light. Thanks for tuning in,
44:04
Speaker 1: See you next time. Thanks for listening, and remember that.
44:14
Speaker 1: Daniel and Jorge Explain the Universe is a production of
44:17
Speaker 1: I heart Radio. For more podcast from my heart Radio,
44:21
Speaker 1: visit the i heart Radio app, Apple Podcasts, or wherever
44:24
Speaker 1: you listen to your favorite shows. Yeah,