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Cool Applications of Light!

Cool Applications of Light!. Fun Fact: For any given medium other than a vacuum, different wavelengths (colors) of light travel at different speeds within that medium! This means that the index of refraction for a substance actually depends on the color of light traveling through it.

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Cool Applications of Light!

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  1. Cool Applications of Light!

  2. Fun Fact: • For any given medium other than a vacuum, different wavelengths (colors) of light travel at different speeds within that medium! • This means that the index of refraction for a substance actually depends on the color of light traveling through it. • Quick Review: • All wavelengths of light travel at the same speed in a vacuum. How fast do they go? • 3 x 108 m/s • For all other media, will light travel faster or slower than this speed? • Slower!

  3. This property of light is called dispersion. • The color that refracts the least from its straight line path is red. • The color that refracts the most from its straight line path is violet.

  4. What makes diamonds sparkle? • How do fiber optics keep us communicating? • How do those cool holiday decoration light up? • When light passes from a more dense medium (high n value) to a less dense medium (lown value) at a certain angle, all light is reflected back into the first medium and there is no refracted ray. • Let's see it!

  5. This property of light is called total internal reflection. • The angle at which this will occur is called the critical angle. • TIR results in a refracted angle of 90°. • This means that Snell’s Law for TIR is: • n1sinѲ1= n2sinѲ2 • n1sinѲc = n2sin(90°) • n1sinѲc = n2(1) • sinѲc = n2 n1 Make sure your calculator is in degree mode!

  6. Examples • What is the critical angle for light traveling from diamond (n = 2.42) to air? • sinѲc = n2= 1.00 Ѳc = 24.4° n1 2.42 • What about diamond to water? • sinѲc = n2= 1.33Ѳc = 33.3° n1 2.42 • What about water to diamond? • Not possible!

  7. Demos

  8. Rainbows are a result of both dispersion and total internal reflection. • (White) light from the sun enters the front surface of a raindrop • It is dispersed or separated into its composite colors • As light hits the back surface of the raindrop it is trying to go from a more dense medium (water) to a less dense medium (air) at an angle beyond the critical angle • TIR results and the light is sent back towards the front of the drop where it is refracted again

  9. Each part of a rainbow that will form depends on the angle at which the drop is located to us • From your perspective, red will always be visible at the top of the rainbow and violetat the bottom

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