Refraction occurs when light waves bend as they are passing from one medium to another.•Causes a change in:Causes a change in:

– SpeedSpeed– WavelengthWavelength– DirectionDirection

•the frequency of a wave remains constant therefore, consistent w/the wave equation (V = ƒʎ), wavelength must change.•In a vacuum, all EM waves have a speed (c) of 3x108 m/s. In other materials, light light slowsslows downdown.

In which way does a light change as it travels from glass into air?

a. Frequency increasesb. Frequency decreasesc. Speed decreasesd. Speed increases

• The index of refraction (n) index of refraction (n) is a measure of how much light slows down in a material. –The number describes the ratio

of the speed of light in a vacuum to the speed of light in the new material–The slowerslower the wave moves in

the material, the largerlarger the “n” value

Crown Glass Crown Glass is n = 1.52, meaning that light travels about 1.5 times slower in crown glass than in vacuumThe index of refraction in a vacuum is n = 1.00000 (speed of light at full capacity)

n2 = 1.5

n1 = 1.0

A

B

A light ray traveling from a fastfast toto slowslow medium ( low “n” value to high “n” value)

will bend towardstowards thethe normalnormal

A light ray traveling from a slowslow toto fastfast medium (high “n” value to low “n” value)

will bend awayaway fromfrom thethe normalnormal

Arthur Podd's is spearing fish while standing on the shore. The actual location of a fish is shown in the diagram below. Because of the refraction, the observed location is different than its actual location.

•Indicate on the diagram the approximate location where Indicate on the diagram the approximate location where Arthur observes the fish to beArthur observes the fish to be•Must Arthur aim above or below where the fish appears to Must Arthur aim above or below where the fish appears to be in order to strike the fish???be in order to strike the fish???

This is not This is not really me; this really me; this is my is my IMAGEIMAGE!!!!

Arthur must aim at a position on Arthur must aim at a position on the water the water below where the fish below where the fish appears to be. appears to be.

Since light refracts away from the Since light refracts away from the normal (water to air) as Arthur normal (water to air) as Arthur sights at the fish, the refracted ray sights at the fish, the refracted ray when extended backwards passes when extended backwards passes over the head of where the fish over the head of where the fish actually is.actually is.