WEBVTT - How Light Wave Interference Works

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<v Speaker 1>Brain Stuff is sponsored by Harry's dot com. Get a

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<v Speaker 1>brain Stuff from how stuff works dot com where smart

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<v Speaker 1>happens him Marshall brain. It's very common to see rainbow

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<v Speaker 1>patterns when you look at the surface of a c

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<v Speaker 1>D and also when you look at soap bubbles or

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<v Speaker 1>a thin film of oil floating on still water. Where

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<v Speaker 1>do these colors come from? All three of these rainbow

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<v Speaker 1>effects are created when light waves interact with each other.

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<v Speaker 1>It's known as constructive and destructive interference of the light

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<v Speaker 1>hitting thin surfaces. Think about a very thin film of

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<v Speaker 1>oil floating on water as an example. When white light

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<v Speaker 1>hits the film, most of it passes through the film,

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<v Speaker 1>but some is reflected off the top and bottom layers

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<v Speaker 1>of the film. In the same way. When you stand

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<v Speaker 1>in front of a window in your house, you can

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<v Speaker 1>see a reflected image in the window. Most of the

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<v Speaker 1>light is passing through the window and out of the house,

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<v Speaker 1>but some is reflected back at you. The light that

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<v Speaker 1>reflects off the top layer of a film of oil

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<v Speaker 1>travels slightly shorter distances than the light reflecting off the

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<v Speaker 1>bottom layer. If the film is very thin on the

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<v Speaker 1>order of the wavelength of light, then interference can occur.

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<v Speaker 1>Violet light has a wavelength of about four thousand angstroms,

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<v Speaker 1>and angstrom is a hundred millions of a centimeter, while

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<v Speaker 1>red light has a wavelength of about seven thousand, six

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<v Speaker 1>hundred angstroms, so we are talking about extremely thinned films.

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<v Speaker 1>If the film is just the right thickness, a red

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<v Speaker 1>light wave a side wave will bounce off the top

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<v Speaker 1>and bottom layers in perfect alignment, and the tubers a

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<v Speaker 1>sign ways will combine to double the amount of red

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<v Speaker 1>light scene, or they may reflect exactly out of phase

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<v Speaker 1>and the red light will be eliminated. Because specific colors

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<v Speaker 1>can be doubled or eliminated depending on the thickness of

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<v Speaker 1>the film, it changes the color of light and we

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<v Speaker 1>see colors like colors of the rainbow coming off the film.

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<v Speaker 1>On a CD, the surface is mirrored, so the rainbow

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<v Speaker 1>colors are much more intense. In a c D, the

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<v Speaker 1>angle that the CD is held at controls the colors

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<v Speaker 1>you see. The angle, along with the bumps on the

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<v Speaker 1>c D surface, controls the path difference and therefore the

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<v Speaker 1>colors you see. Do you have any ideas or suggestions

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<v Speaker 1>for this podcast? If so, please send me an email

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<v Speaker 1>at podcast at how stuff works dot com. For more

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<v Speaker 1>on this and thousands of other topics, go to how

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<v Speaker 1>stuff works dot com. Brain Stuff is sponsored by Harry's

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<v Speaker 1>dot com. Get a great evening experience for a fraction

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<v Speaker 1>of the price. The quality of the shave is so

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<v Speaker 1>important that Harry's purchased the factory that makes their blades.

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<v Speaker 1>Fifteen dollars gets you a set that includes a handle,

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<v Speaker 1>three blades, and shave cream. Go to Harry's dot com.

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<v Speaker 1>Use the code brain stuff to save five dollars off

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<v Speaker 1>your first purchase.