Or you see a child blowing bubbles, great big bubbles, and the bubbles floating off in the wind, yeah . And you look at the bubbles and you seewow, what you see . Beautiful rainbow colors in the bubbles. You see the spectrum. You see all the colors reflecting from the bubbles. Isnt that right . Or sometimes you take, like, an abalone shell and you hold up the abalone shell and you see the beautiful colors. We call these iridescent colors, yeah . And youre looking at the shell and then you turn the shell a little bit andhey, wow, the colors change a little bit. Or sometimes on a rainy day, you look at gasoline on a wet street. And you look at the gasolines splotches andwow, man. They have beautiful colors. And there are rings of colors too. Do you have another the rings go all the way around like you got green. The green will continue and come all the way around. Its sort of like a contour map, a microscopic contour map of the different elevations of the gasoline on that wet surface. Whenever you have a double reflection like that, oftentimes i should say, when you have a double reflection from two surfaces, these double reflections give you beautiful colors. We call this interference colors. We talked a little bit about interference before, gang. Remember . Lets briefly review that interference of waves. Consider a wave like this maybe, yeah . Now, consider another wave locked right on top of it. Same frequency, same step, physically say, same what . Phase, okay . Right in phase. Those two waves will add together to be what . A wave of greater amplitude. Greater amplitude, same frequency, okay . No big deal, but how about this . Consider a wave and another wave starting maybe here. You know, starting at a different point. That wave is out of phase. If its halfstep out of phase, was he in a 180 degrees out of phase. These two waves are out of phase of one another, 180 degrees. They combine to produce what, gang . Aint that nice . They cancel out, okay. One wave cancels another. The same thing happens with light. I can show you what i mean with this laser. Im gonna shine a little laser spot on the wall. Ill put the lights out. You guys see that some places there, its very, verytheres little dark spotssplotches. And some places is very bright . Lets talk about that and see whats going on. What happened here now, gang, is the lights coming through piece of glass and the glass is irregular and its kinda fanning out and making a spot on the wall. But theres bound to be some places with that light comes in phase here with maybe another point over here. That they come right in the phase and be extra bright. And right down below it might be light coming in like this and light coming in from another little part of that little lens really there like that. And when those two gang up, guess what they do, gang . Begin with co. Cancel out. Cancel out. And over here, they add up. So over here, youd have a region thats dark, okay . And that little dark region is the result of light interfering, okay . Destructively. Over here, its light in deferring constructively. So you get those bands or those little splotches because of the light interference. You get the same type thing with gasoline on a wet street. Heres some light reflecting off some water, okay . Light reflects off the water and your eye is up here and your eye sees the light. Lets suppose this is blue light, pure blue light shining down, okay, shinning down on some water and bounces off and gets into your eye. Let me ask you a question. What color would the eye see . Blue. Its an easy one. Begin with blue. I got b. Begin with b, okay . You can see blue. You can see blue, right . But lets suppose its not shining on the water. Lets suppose its shining on gasoline. Now, what color is the eye gonna see . Blue. Begin with b. Blue. Blue. Its still gonna be blue because its reflected and we know that light doesnt change its frequency when it reflects. If you got a blue shirt on, you stand in front of a mirror, what color is the image . Blue. How about a red shirt . Red. Could you do green . You get the idea, okay. Light doesnt change frequency when it reflects. But what if this gasoline is floating on a surface of water and it will do that. Now, youve got two surfaces. Some light is reflecting off like this, but some of that light goes down through and reflects off the water surface. And if it does that in such a way that this distance puts the reflected wave 180 degrees out of phase or out of phase 1 2 step. Then when it gangs up with this one, whats it gonna do, gang . Whats the eye gonna see . Nothing. Nothing. The eye is not gonna see light. The lights cancelled out. You see that . Now, how thick this is has to do with the wavelength of light while what work for one thickness wont work for another. And it has to do with whether or not the light changes phase when it hits the different surfaces . Im not gonna get into that part now. Its footnoted in your text. Suffice to say, light from a double reflection might have such a distance extra distance that by the time it gets back up here, its out of phase with the part the reflected from the top. That is destruction interference. The eye gonna see nothing. Youre not gonna see this in your local environment. What you will see in your local environment is white light from the sun. The sunlight coming down and hitting the gasoline on a rainy day. Youve all noticed that. You notice that . Its gotta be a rainy day that the gasoline gives you the color. Why . cause the gasoline gotta float on water to give you two surfaces to make reflection from, yeah . Okay . Now, when white light hits for this particular thickness, the blue is gone. You check with your neighbor and see if your neighbor knows. If the blue is gone from the white reflecting, what color is the eye gonna see . Go. Whats it gonna be, gang . Green. Something. How many say a yellow or an orange or Something Like that . Yeah, yeah the complementary color of that shade of blue, yeah . We talked about this. We talked about the blue sky, remember . The blue sky scatters off blue. So given enough sky for the light to get through by the time light gets to you and all the blue is scattered, what do you get left, gang . You get the complementary color. Okay . Sorta like the orange or the yellow, yeah . So when you take one color out of white light, what you see is the complement, huh . In the same way, the water absorbs the red and so what do we see the red . We see the and what do we see the water . We see the water of cyan, the complementary color. Same type thing here. Now, if you understand that, you can see this. Lets suppose the light is coming down. The same thickness of gasoline now, but the light is coming down on a more grazing angle and bounces to your eye. You could do that by taking your eye and say, hey, i see it sort of a yellow. And you got on like this and all of a sudden, oh, it changes to a different color. And some say, how come it changes . And you say, what is no reason for that. Its different angles, different colors. Maybe thatscome on. Why does it change, gang . The apparent thickness would be greater. Wouldnt it . Yes. If youre coming in at an angle like this, isnt that a thicker path than this one here . Huh . Huh . Its like a worm crawling through a book. The worm crawls from the book, from here to here and says, hey, pretty short book. Now, you hold the book like this and the worm crawls through, as itmy gosh, an encyclopedia, okay . You get a different apparent thickness for the way you hold it, yeah . And the same thing would happen with light and so light coming in like this. You would cancel a longer wave or a shorter wave . Neighbor . Through a longer path, would you cancel a longer one or a shorter one . A longer one. Longer one. So let me ask you a question, gang. Lets suppose you happened to cancel out the yellow. And where youre seeing, honey, you aint seeing the white light, you seeing the white and the yellow aint there anymore. The yellow have been cancelled. What color your eyes see . Check it. Whats the neighbor say . If you cancel the yellow, the eye gonna see what . Blue. Blue . Can you see its blue . Get it . Magenta. This saturday night, when you take your bath, use some soap. In fact, splurge. Use bubble bath. Get a whole lot of bubbles in your bathtub. Now, youre taking your bath and your light up above, theres an incandescent lamp, white light, okay . White light shining down on the bubbles. Take a look at those bubbles closely. Guess what, gang . The highlights aint white. The highlights are all different. Colors. Hue. How many have noticed that already . How many people have taken baths year after year after year and never looked at the bubbles . Look at the bubbles on saturday night, and see if you dont be seeing the bubbles got different colors. And your friends say, how come the different colors . And you say, thats an example of . Physics. Begin with i. Interference. Interference. Interference, thats right. You got a bubble like this, maybe you got the white light up above, okay . Okay. And the white light coming down heres your eye right here. Light come down, hit the bubble, bounced to your eye, yeah . But some of that light bounces from the bottom surface and goes to your eyes. Is that right . Right. Arent there two surfaces to that thin bubble in the way that thing filled . Two surfaces. Part bounces from the top surface, part from the bottom. Hey, what if that extra distance going down through is such that it will cancel out one of the frequencies over here . Then, honey, that eye aint gonna get it. Now, if you got white coming down, theres no cancellation. Youre gonna see white. But if one color is canceled, youre not gonna see white. Lets suppose the color thats canceled happens to be red. Then the eye will see what color for that particular bubble . You guys know your color rules . No. You gotta know what the complementary color of red is. We take all the red away, what do you got . Green. You get that green cyan. You got that cyan, the greenishblue. So the eye over here is gonna see what . Greenishblue, all right . Now, you point to the bubble and you say, hey, thats a greenishblue bubble right there. Right. Your friend. Your friend looks down. And your friend looks at the same bubble. But for your friend this is a different thickness being canceled. Maybe this different thickness, maybe whats being canceled here is the yellow. And so your friend sees that light, white minus the yellow, you say, hey, look at the greenishblue bubble. And your friend says, no, it aint. Its a. Yellow bubble. Blue bubble. So your friends says its blue, you say its cyan. Whos right . Me. What happens in the tub . I say its cyan. I say its blue. I say its cyan. Wham, boombubble bath. Okay, see whats happening . What color you see depends upon what . With everything. What you see depends upon what . Do we all see the same thing . No. Huh . Depends on your point of view. Open up the hood of a car, have the mechanic look at it. Now, you look at it. You see the same thing . You see the same thing . No. I remember years ago, a guy was passing around a picture of his girlfriend, says, hey, you wanna see my girlfriend, man . Look at this. Takes out this picture, he shows the picture. And were all looking at were feeling sorry for him, you know . [laughter] andbut to him, to him, hesthats my girl. And were like, oh, my god, pretty. And you start to wonder, do we really all see the same thing, huh . Huh . Over here, these the different bubbles depend upon your point of view, where your heads at, right . What you see depends upon where your heads at. Think about it, gang. And you get the different colors. You know these camera lenses . You see these camera lenses. You see that violet hue on the camera lens . Ever see that, coated lenses . And they look violet, dont they . Do you know why they look violet . No reason for that. Its just one of those no, come on. You know why they look violet . Theres a color being canceled. Theres a color being deliberately canceled. And the color being deliberately canceled is a color that were most sensitive to. And if we wanna cut down that reflection in that lens so we dont photographed by film, and we can only do it for one color. Were gonna pick the color that the eye is most sensitive to, that the sun is emitting mostly of. And what is that color, gang . Begin with a y, end with mellow. Try it. Yellow. Well, all right then, yellow. Try it. Yellow. Good, good. Okay, we got it. Okay . Heres what happens. Have these lenses, camera. Heres what the problem is. Light will be coming in, and come to focus right there, and thats nice cause you got your camera film right there, and you want the cam to focus. But some of the light reflects off. It comes out, you dont care. But then comes back in, reflex out, you dont care. And then comes over here. And part does this. And that comes to focus here. And so whats it gonna do is photograph your film. You dont want that light getting there. You like to get rid of it. Theres a way to get rid of light. You can cancel it. So what you do, at least for the yellow part, you can put a thin film there. And that film is onequarter the wavelength of yellow light. So the light that bounced from here also is ganged up by light that goes here, a quarter, a quarter, a half. And what happens is youll cancel it out. And so that thin film will cancel all this. It wont happen, and youll be back to your nice, sharp picture, at least, for the part of the light in the middle of the spectrum. So you, out herelook at the thinthis little thing. If its canceling yellow on this side, its canceling yellow on this side cause its the same type of thing. Youre getting a double bounce out here. So when you look at that purplish surface, okay, that purplish surface of the lenses, it isnt like they got some purple gunk they put on there. No, no, no. Its very, very clear. But the thickness is such that it will cancel out the yellow and give you the complementary color, so you see your coded lenses, the nice purplish color. Aint that neat . You like . Yeah. Yeah. I bet gang, well talk about polarization. We talked about charged polarization before. We talked about, like, negative, being on one side of a molecule, positive, on another. Polarization, in this sense, is altogether different. Were talking about the lineup of waves. If i take a rope and tie it to the wall, and i shake the rope up and down like this, guess which way the wave will vibrate. How many say, oh, probably like this . Hey, come on, come on. Trick question. No, no. If i shake it up and down like that, the rope will vibrate like that. And the vibration is aligned. We dont say aligned. We say its polarized. If i shake the rope back and forth horizontally, then ill generate a horizontally polarized wave. Okay . You saw the example in the textbook. If i pass these waves through a picket fence, maybe the picket fence can filter them out. It turns out, if i have a picket fence where the fence stakes are all vertical, i have vertical openings. And i shake my rope, and it goes right through the opening. Its like the opening werent there, the shake goes right on through and the wave travels. Thats easy to see. It is very conceptual. If i take the rope and shake it sideways however, it cantthe vibration cant get through the fence. And so what the fence does is it blocks it. And so thats a filter. And i have over here such a thing. Heres a polarization filter, okay . And thats what this is. This will allow light to vibrate through going only one way, not another way. I dont know what the plane of this is. I cant see. But the and lets suppose its like this. I have microscopic picket fences like that. I have in the back here a piece of white material that would diffuse light, so that when i shine light through it, it wont there wont be too much glare. But nevertheless, this is a piece of polaroid filter. And let me tell you how this came to be. It turns out that noncubicshaped crystals, all noncubic crystals say, Something Like this or like a diamond shape. All nontransparent crystals will pass light in two directions, the two preferred directions. The crystalline structure is, sort of, like an orange grove. Have you ever drive by an orange grove to see all this you see right down . And youre driving right down the cliffs, okay . There are certain preferred paths. Well, it turns out, light will go through vibrating like this, and light will go through vibrating like that. And over here, no. Youd only get components here and components here. And it turns out, in most crystals, the vibrations in one direction go through quicker than the vibrations in the other. So theres little time delay. And you get beautiful colors as a result of that. Get into that a little bit later. But, for now, there are some crystals that take this one here and cut it right down, and its absorbed. This was known at the first part of the century, a lot of people knew that, that they were needleshaped crystals that would pass light in only one direction, one direction only. A fellow by the name of edwin land knew about that and did something about that. What edwin land did was took all these crystals, this crystalline material, made into, sort of, like a jelly, put it on some cellophane and stretched it. And when he stretched the cellophane, guess what these things here did. What would happen if you held a whole bunch of needles, a whole bunch of needles on a piece of plastic and they point every which way . And you take and you stretch the plastic out. What will the needles do, gang . Wont they kinda all line up . Thats what land did. And he got them all to line up. And then what he did is he put it down, hed put another piece of plastic on top, took his wifes iron and ironed it, and cemented those needles to and made a million more than a million dollars. Edwin land patented it. And these are polaroid filters. And thats what they, in a sense, are cause theyre made up of molecules in here which are crystal little crystal the crystals or molecules that are all lined up in one direction and will allow the light to pass through one way. I can kinda show you that with a lamp here and using tools. You can still see the light. These things must be lined up. Whats coming through one comes through the other, but let me turn it. What happens right in there, gang . Right in there. Can you see that the light doesnt come through . Or i can hold this like this and just turn this. Comes through, comes through, comes through, doesnt come through. Not so much, no much and now its blocked up. Aint that nice . Now, hc. How come . This is easy to see. It requires a knowledge of vectors, the arrows. Lets take a look. Lets suppose my lamp, my original polaroid, is like that. Light coming through. What kind of light can it come through, gang . Light hitting it is like this. Like this that hits it but the only part that comes true is the part vibrating like this. So what comes through is light vibrating like that. When i put the other polaroid in the way, the square piece, what happens if well, lets try this first of all. What happens if this and this are lined up . Will these vibrations get through there . Yeah. Is the vector falling right through there . Andhowd it comes . So the light is not cut out. What happens when i rotate it 90 degrees . Okay. Is there any component of this along that direction . When we talked about the bowling ball before in the ally, pulling full straight down, a vector straight down and we said this. Is there any component 90 degrees to it . And the answer begin with a n. No. Same type of thing, see . We got a vector, vertical, theres no component there so nothing gets through. Thats what you saw. Whats kind of interesting is an angle. Lets suppose i put this on an angle. Now, this falls on top of there. As you recall, did any light get through . No. Yeah. Some got through. And heres where your vectors come in. This vector here has a component on this direction and a component on this direction. Guess which component wont get through. This one or this one . This one. That wont get through, see . And you guys remember this . You take a little component here, huh . And heres a other component here. And this vector here behaves as if its really this one and this one at the same time. This one doesnt make it, but this one does. And look what, some comes through. This one is not as big as this one. Did you notice the light was not as bright so the light is dimmer . But never the less some comes through. And rock this all the way around, this component keeps getting smaller and smaller, smaller and finally shrinks to zero, and whip, boom, nothing gets through. So thats happens to these polaroids. Kinda neat, huh . It turns out that when light reflects from surfaces at a grazing angle, the polaroids component is preferred, you know . If youre like driving and you have a road surface and the light is coming down, hitting, it turns out the light that would make up the glare is polarized in the same plane as the surface. Do you ever take these scaly rocks and go out in a pond and you get flat rocks, you wanna scale on across the surface . If you take the rock and you throw it kinda flat, sort of like this, okay . It willbounce off, yeah. How about you throw it like this . Kinda go down, yeah. Light does the same thing. Light is coming down like this bounce, huh . Light is coming like this gets absorbed. So thats why you get the glasses. What kind of polaroid glasses would you wear to cut out glare from horizontal surfaces . Let me show you three pair. Which would you use, gang . This, this or this for driving. You are a truck driver and you gonna ride along the road, which pair of polaroids . How many say theyre all the same . How many say id wear these ones here. Squint city, honey. Whats gonna come through those glasses . Polaroids light. You got to drive like this, okay. [laughter] a cup of coffee, please. Okay. Occupational you no, this is what you get. See. Theyeah. The polaroid glasses that you buy are usually like this because most of the glare comes from horizontal surfaces. What if youre a painter all the time . You paint in vertical surfaces then you probably wear glasses like these. I dont where do you get them. Okay . But usually the glariest polaroid is horizontal so we cut the horizontal off like that. Youre gonna like that, honey, that light came inits okay. Butand now what you see is without glare, hmm . Do you know what this pair are for . 3ds. 3d movies, used to be popular. Used to be 3d movies where you have two projectors are going one at one time and youve gotta see each scene independently so the polaroids one in this way. You got your glasses that way, the other projectors polarizing this way, you got glasses that way. Boom. Each eye sees an independent view and 3d vision right there. Questions on that. Question. Yeah. Polaroid glasses aint necessarily cut out uv, though, right . No. Polaroidthe function of polaroid glasses is to cut out the horizontal component of all light. It turns out all glasses will cut out uv, all glasses. Now, what part of the uv . Very, very close to the visible part, a lot of glasses will transmit. But the High Frequency uv, the kind is dangerous, all glass. And i believe most plastics will cut it out. So anyone thats wearing glasses, you dont have to worry about uv light hitting your glass. Any kind of glasses. Have you heard of the blublockers . The blublockers. I havent heard of the blublockers. A new kind of glass . Yeah. Supposedly, it cuts back on the little ray side . Do you pay more for it . I dont know. I dont have them yet. I mean, theres a lot of things that these glasses will cut out the uv. Well, honey, what glasses wont . Okay. You know what im saying, so i got a question for you, gang, something nice, keep you entertained a little bit. See this . Okay. I remember the first time i saw what im gonna show you now. A fellow came in my office when i was a graduate student and he had three sheets of polaroid. Ive never dealt with three sheets. Two is enough, yeah. And he had three sheets. And he says, hey, hewitt. If i take this third sheet and i put it in front, will light come through . I said, nwh. Right . Okay. Here, how about if i put it in the back, will now they come through . And i said nwh, right . He says, how about if i put it, like, in between the two, will light come through then . I said nwhyeah . Theres your light, honey. Whats this nwh . Can you kinda see that . Light is getting trough. Thats sandwiched in between. Over here no, no, yes. To understand that and explain that, you need to know something about vectors. You guys, have known about vectors . Could you kind of make a little vector diagram showing that how are light does get through . I think you can all do it particularly if you Pay Attention to your textbook. All right . And can you do that and hand that in next monday . Okay. Okay. Okay, great. All right, physics. Catch you later. Welcome to another session of beliefs and believers. Im dr. John simmons, and as happens, we are moving into another dimension, the ethical dimension. And in many ways, when we speak of ethics, it cuts to the core of this course, as you probably know by now, because were talking about behavior. What people believe well, weve seen many, many different examples of it. But how they behave proper patterns of action thats what we want to look at as we move through this very, very important dimension, because you know, believing,
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