Were talking about electricity and magnetism. Remember that time i took the rubber rod and i charged it up, okay . Well, pretend this is the rubber rod charged up. And now i shake it through space. When i shake it back and forth, is that not an electric current, charged in motion . What surrounds an electric current . Begin with mf. Magnetic field. Magnetic field. How many say, oh, that Magnetic Field is probably very, very steady . How many of you know the Magnetic Field changing . Whats a changing Magnetic Field induce . Begin with ef. Electric field. Electric fields. Whats a changing electric field induce . Begin with mf. Magnetic field. How many are starting to catch on . What does this changing Magnetic Field induce . Begin with ef. Electric fields. What does the changing electric field induce . Begin with an mf. Magnetic field. How many are getting the idea . Okay. It turns out these waves will regenerate one another. So if you have a shaking charge, honey, you get electromagnetic waves throughout space. Where the electric field makes the magnetic the electric, magnetic at the speed of light thats what light is. Thats what light is. Light is electromagnetic wave generated from a shaking charge. If i take this stick and i put it in the water, and i shake it back and forth, wont i disturb the water . Wont water waves travel out . You can understand that. But what im saying is you take a charged object. Well, just take a charge, shake it back and forth and guess what you generate, gang. Begin with a w. Waves. Waves. And these waves are electric and Magnetic Fields, so guess what kind of wave. Electromagnetic. Electromagnetic wave. Thats right. And thats what were gonna talk about now. Electromagnetic waves and the very, very small part of the electromagnetic waves. You get the whole spectrum of waves. Lets start way down with the radio waves, really long, long waves. And the radio and the frequency will get a little higher, a little higher. And pretty soon, those waves for example, your radio antennas downtown are shaking waves up and down like a few millions times per second. Thats your fm waves. A few thousand times per second, thats your am waves. But if you shook the electrons in your radio antenna up and down like a million, billion cycles per second, honey, the waves that are generated are gonna activate what . Begin with ey and get the e on the end of it. Eye. Your eye, thats right. [laughs] remember we had the tuning forks that time and hit one tuning fork and made the other one ring . Well, in your eye, you got tuning forks there too, and guess what frequency they ring at, gang . Million, billion cycles per second. Million, billion hertz and thats light. And light, when that light comes in your eye, it makethat sight. Would you like a profound statement for a party sometime . Sure. When you want to say something, and everyone will say, wow, heavy, man, heavy. [laughs] would you like that . Would you like to hear one . Yes. Here it is. You probably will want to put this in your notes. Here it is. Light is the only thing one can see. [laughs] ooh. You saw a lot of substance to that, huh . Would you like another one . Yeah. Just as good . Sound is the only thing that one can hear. Ooh. You have people following you after that. Theyd say, hey, this guys dude is heavy, okay. You get the idea. Anyway, we get all these waves, gang, and a little narrow, narrow, narrow band of those waves, starting off with the low frequencies that look to the eye to be a color. Guess what the color be for the lowest frequency . Begin with an r end with a d. Try it. Red. Excellent. Red. And then lets shake it a little bit more and guess what the frequency is. Orange. Orange. Okay, some people. Shake it a little bit more. What color are you gonna get . Yellow. A little more. Green. More. Blue. More. Violet. More. Indigo, black. Violet. Violet. You cant be seeing. You cant be seeing it, okay . Thats not light anymore. We call it beyond the light. We dont say beyond. Some would say, what is beyond the violet . We dont say beyond the violet. What do we say, gang . Ultra. Ultraviolet, okay. And those waves you dont see. And many even go further still, higher frequencies like xrays. When xrays were discovered, it wasnt known what they were. So guess what they call them . No, not y, not z, but what . X. And it turned out, lo and behold, xrays are High Frequency electromagnetic radiation. And then beyond the xrays, you get whats called gamma rays. But theres a whole smishsmash of waves, okay . Less than 1 we can see, and we call that light. Here, gang, i have a prism, all right. This is a prism brought in by roger, okay . This is a roger prism, all right . And this prism will also take the light and bend it into a rainbow. Later, were gonna take some white light shining in here, and, boom, youre gonna see on the other side, what . Begin with r and with b. Rainbow. A rainbow. And that rainbow is another word for spectral spectrum of colors, yeah . And this will give us spectrum of colors too. It turns out it will give a spectrum of colors because it turns out different colors of light will travel at different speeds right. Through this material or any material. Did you guys know the speed of light is less in glass and water than it is in air . And how come the light slows down when it gets to the glass or when it gets to the water or anything . And heres another thing. This used to bother me years ago. If the light slows down when it gets in the glass, hows it speed up when it comes out the other side . It seemed if you want to get light to slow down, get it on a piece of glass plates and at the end, you can just catch it in a bucket. That keep dribbling down, yeah . But how does the light speed up again . How does light get through glass . Let me give you a little scenario of Something Like how that works. Light is a throbbing spark of Electromagnetic Energy, huh . And that throbbing spark of Electromagnetic Energy has a certain frequency, at a certain frequency at which it throbs, yeah. And when that, whoom, hits into a piece of glass, that glass got any atoms in there . How many say, oh, no, the glass probably dont have any atoms . Come on, the glass got atoms. And whats the atom have around its nucleus . Begin with e. Electrons. Electrons. And guess what those electrons will do when that Electromagnetic Energy hits it like this. Hit, boom, theyll start moving the same way. Theyll be set into vibration, okay . Now, whats a vibrating electron do . Oscillating. Did we talk about that before . Whats a vibrating electron do . What does it emit . Oscillates. An electromagnetic wave. So that light will be captured by the atom. And them, boom, the atom will vibrate. And, foom, send out its own light wave. That catches the next atom. When that light wave hits that atom, whats that atom do . How many say, oh, it probably dont vibrate . Come on, it vibrates, too, all right . So, boom, its absorbed. Now, whats the vibrating atom do . Boom, spit, burp, bam, bam, bamit cascades, when it gets to the end. Heres your piece of glass like this, yeah. Heres your first atom just sitting like that. Here comes a wavechoo, choo okay, hoop, i spit. Next atom, boom, okay, boom. Hit, boom. Heres the atom right on the edge over here. Whip, boom. This one, hit, boom, and then foom, free space. How fast did it throw it out . Free space. You know what the speed of the light was in between atoms . 300,000 kilometers per second, the speed of light that you get in a vacuum. cause guesswe think of a vacuum as void, right . Take a piece of glass, take a piece of water, whats in between the atoms . How many say airspace . No, no, no, no, no. No airspace. Whats in between there, gang . Begin with a v end with oid. Try it. Void. A void. And guess how fast that light wave go or that light particle or that light goes in between atoms . The same as it goes outside. How come light slows down when it goes through . I wonder there could be maybe a time delay between being absorbed and spitting it out. If there is a time delay, wouldnt that, in effect, slow down the light getting through . Hmm . Lets suppose i have, like, a little toy soldier that can walk like this. And the toy soldier walks at only one speed, only capable of one speed, okay . Lets suppose that toy soldier walks over and touches another one, choo, choo, choo, choo and the other one starts walking, choo, choo, stops. Choo, choo, choo, choo. See what im saying . The toy soldier that comes out the end here is not the toy soldier that went in. You see that . A little time delay. If theres a lot of interactions, does that mean a lot of time delays . That means a color of light that would interact a lot will probably move slower than a color of light that doesnt interact so much. Does that make sense . And guess what color of light interacts a lot with glass. Violet or red . Violet. Blue. You dont be knowing that yet. Let me tell you something. The resonant frequency of the electrons in there are like ultraviolet. And when ultraviolet light comes in, and hand, when that sets that electron in the move and, it is really moving so much it bangs into everything else. And the energy degenerates into . Begin with a h end with a t. Try it. Heat. Heat. And all that ultraviolet light gonna do, honey, is heat up that glass, because its hitting that resonance. The resonance, the vibration is too much. So the resonant wont get through. But whats below that ultraviolet . Begin with a v. Violet. And that violet is close to the resonance. And the vibrations arent enough degenerated the heat, but enough to interact here, here, here, here, here, here, all the way. And by time youviolet light is gonna take a long time to get through. Red is way, way, way down underneath. You could, kind of, look at it like this, most of your atoms wont even do a darn thing when red comes by. So red just, vroom, skates right out by and only interacts here and there. Guess which color should get through fastest . Red. You see its red . And a term were gonna learn later on that when the different speeds will bend different amounts. And thats why this and rainbows you see above you, display the colors that we see. It has to do with different colors bending. And we know why they bend differently, because they got different speeds in the medium, different average speeds. The sun beats down, emits light. Why does the sun emit light . Honey, those electrons in that sun are shaking like crazy. All kinds of frequencies, okay . And so what you get is you get all kinds of frequencies of light coming down to us. And if we made a graph of the frequencies of light versus the brightness, wed get Something Like this. Wed get Something Like this. Over here, you cant even see, thats the infrared. Over here, you cant see, thats the ultraviolet. But it turns out that right in here, thats the frequency of light that most ofthat is emitted mostly by the sun. And thats right in the middle of our color spectrum. Because we start down here with red, orange, yellow, green, blue and violet. And guess whats right in the middle, gang . Begin with a g, end with a een. Try it. Green. Excellent. All right, all right. Green. Its green. Green is right in the middle. It turns out a yellow green. A yellow green is what most of the sun emits mostly. Its like a chartreuse. When i was a teenager, honeys, i had a chartreuse convertible. You could see that thing 15 miles down the road, okay . And you know why you could see it so well . Because most of the light from the sun is that color, and guess what we have evolved to see best of all . Take a guess. Yellow green. Yellow green. We used to call it chartreuse. Is that what why they paint fire trucks that color these days . Did you notice that, paul . What are the new fire trucks . They used to be red. What are the new ones . Yellow green. Yellow green. And why they be yellow green, honey, huh . Why . Because you want to see those things coming down the road. And so they find you and said, hey, lets paint them a color that human beings can see the most. And, yeah. Do you notice the color of your street lights . What color theyd be, gang . Yellow. Yellow. A little greenish, a little yellow greenish, mostly yellow, right . Why the streetlights yellow . They used to be incandescent lamps that used to glow white. Now, theyre making them yellow. One strong reason it has to do with, guess what we can see most . Yellow and green. Lets suppose you got a hundredwatt lamp, and its white. And youre saying that a lot of this is coming out, and a lot of this too, right . So youre spreading it along all of that, right . Lets suppose you got a hundredwatts only of this. How about your eye, honey . Youre gonna see more light, because its hitting right where you can see best. Now, those yellow lamps arent very good for your complexion and that sort of thing, all right . But when youre driving at nighttime youre not into that. Youre into whats on the road. You really want to maximize seeing. And, hence, thats one strong reason for the yellowgreen lamps. And the yellowgreen fire trucks. But, suffice to say, we could break this up into three regions. Thats what happens in your eye. The low frequencies average out to be red. The high frequencies average out to be blue. Guess what the middle frequencies average out to be. Irish, what is that . Now, try it. Green. Green. Very good. When youre looking at your Television Set at home, gang, youve only got three colors of phosphorous that give you all that spectrum of color. And what are those colors, gang . Red, green and red, green and . Blue. Yay. And i can, kind of, show you that over here with this light box. Do you want to be seeing such thing . Lets try this. Can weted . All right, gang, what color is that . Beginning with a b. Blue. How many dont even need a hint . [laughs] hey, but you guys are calling that blue, right . Can we be sure that everyone is seeing that color . Didnt you used to wonder that when you were a kid . When daddy said, thats blue. And you wondered your sister called it blue, too, didnt she . But how do you know that she wasnt looking at this, and she learned to call that blue . Do you ever wonder about that . Do we all see the same, mm . Do we all taste the same . Do we all smell the same . Do we all feel the same . Differences, individual differences, huh . And how would you know . And look at what we got here, gang. Red, green, blue, all together give what . Begin with a w. White. White. And isnt that nice . Isnt that nice . Because now what youre doing is the low frequency part of the spectrum, right here, banging into your eye, the middle part of the spectrum, whipboom, banging you right in the eye and the high part of the spectrum, whoop, and it all averages out to be the light isnt that neat . Theres another thing, too, thats kind of neat. Notice that the blue and the green mix together to give bluish green. Isnt that wild, huh . Isnt that wild, huh . Wild. And notice that the red and the blue mix together to give a bluish red. Isnt that wild . Wild. No, thats not really wild. You would expect that. But how about this, the red and the green, where they overlap, they give yellow. Wow. Hc. Why should they give yellow . Now, you mix red and green paint. You get, like, brown, okay . [laughter] but thats color by subtraction. Read the chapter on that. Here we have light on top of light. And red and green hitting your eye at the same time, gonna give you what . Yellow. Yellow. Why . Primarybetween the two. Thats right. Yellow is right between the two. And these are gonna average out to be that, okay . Isnt that nice . Isnt that neat, gang . Anyway, yellowits oh, look at this. We talked about three colors, red, green and blue adding to give white. Is there such a thing as two colors adding together to give white . Answer end with a p. Yup. Nope. No. Try it. Nope. Nope. No, not a pe. Just a p. Yup. Yup. Yup. Okay. It turns out two colors can give white. Can anyone tell me what color mixed with blue will give white . Yellow. Yellow. Do you see it . Yeah. How many cant reason this . Well, the yellow is the red and the green, huh . Okay. Well, let me ask this, what colorred and what color will equal white . Cyan. Bluish green. Cyan. This color here, greenish blue. We dont call it greenish blue. We call it, what . Begin with a c. Cyan. Cyan. Thats right. And how about this, magenta, we call it. Magenta and what give white . Green. Green. Thats right. Heres an interesting thing. Can you do algebra . White take away red equals what . Three. [laughs] white take away red. Cyan. Gives cyan. Shall i do that again . Yeah. Theres your white. Now, im gonna take the red away from it. Watch where my finger is. Ill take the red away. Whoops. [laughter] and whats it turned into . Cyan. Cyan. Did you ever wonder why the sea water is a cyan color . Its green and blue. How many people have never wondered that . So, well, its cyan no, no, no, no, theres a reason why it had to be a cyan. Can we have the lights please, ted . Sure. It turns out that seawater, any kind of water, absorbs, like mad, infrared. In fact, if you take an infrared light and shine it on water, itll heat up very, very quickly. And it also absorbs a lot of red. So when the sunlight comes down, all the colors, yeah, hits the water. Guess what color gets absorbed more than any other. Red. No. No, not green. Okay. Lets try let me give you a hint then. Begins with r, ends with d. Red. Yeah, red. Good. Okay. Some people said green. It turns out the red gets absorbed. When the red gets absorbed, is that the stuff that reflects to your eye . No, no. Its been absorbed. You cant absorb then reflect. You take your pick, honey. So if the red gets absorbed, what does the white light become . Green and blue. Shall i do it again . Shall we put the lights off and do it again . Yep. And turned no, im not gonna do it again. [laughter] it turns out to be that cyan color, see . If red plus cyan equal white, your problem is whats white take away red . And thats why the sea water is the color a. Isnt that nice . Thats why sea water is that color. Different colors of different temperatures of waters, different nutrients in the water, then different shades of that cyan, too, right . Having a lot to do with different amounts of red being absorbed. So the color you see in things around you are not the colors that are being resonated off. Theyre the colors that thats a leftover of colors being absorbed. You see this green, this cyan shirt here. Guess what color is being absorbed by that . Begin with a r. Red. Red, okay . Now, wheres someone with a you see, this red over here, this red shirt . Guess what color is being absorbed. Begin with a c. Cyan. Cyan. All right. Could you do without the hints . Yeah. Well, no. Okay. You get the idea, yeah . Isnt that kind of neat . Colors, fascinating. Red lamp. What color is the shadow . Black. Black. Why is it black . Because theres no light there. Is that mysterious . No. How many say, wow, far out man. What a shadow. Is this black . We all see its black, yeah . A