bending of a ray of light when passing from one medium to another (at an angle) because the wave changes speed Remember, the medium determines the speed of light.

When light travels from a less dense to more dense medium (light slows down), the ray is refracted toward the normal. Example: light slows down when it passes from air into water n i air i > r water r

i r i < r n Example: light speeds up when passing from When light travels from a more dense medium to a less dense medium (light speeds up), the ray is refracted away from the normal. Example: light speeds up when passing from glass into air air i n r glass i < r

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Multiple medium refraction More Refraction Multiple medium refraction

Refraction is responsible for the separation of light into colors, because shorter wavelengths refract more than longer wavelengths. Violet refracts more than longer red

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The properties of light responsible rainbows are reflection and refraction.

Mirages When air near ground gets very hot and causes light to refract (bend) upwards

speed of light in a vacuum (c) speed of light in that substance (v) index of refraction (n) speed of light in a vacuum (c) divided by speed of light in that substance (v) n = c / v

The larger the index of refraction, the slower light travels through the substance.

Total Internal Reflection When the incident angle becomes very large, no light can be refracted. All light is reflected back to the original medium. The light appears to be trapped. Fiber optics transmit information through total internal reflection.

Lens Math Just like mirrors and

Lens Math Signs f = focal length (+) converging lens (-) diverging lens do = object distance (+) in front of lens (-) in back of lens di = image distance (+): In back of lens (-): In front of lens

Microscopes and Telescopes Compound Microscope Refracting Telescope

Eyeglasses A Healthy 20/20 eye Hyperopia – corrected with a converging lens Myopia – corrected with a diverging lens

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Practice Problem A real image is produced by a converging lens with a focal length of 15 cm. If the object is 10 cm tall and 21 cm in front of the lens: Where is the image located? How tall is the image? Is the image magnified or reduced?

Soap Bubbles (and other thin films) The properties of light responsible for the separation of light into colors by a soap bubble (or other thin films) are reflection, refraction, and interference. Interference is defined as the result of the superposition of two or more waves.