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AP® Physics 1 & 2

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Moderate

Meaning of Critical Angle

APPH12-WXG9NI

The critical angle for water is ${ 49 }^{ o }$. A ray of light initially moving upward in a sample of water toward the air atop the water is incident upon the air-water boundary at an angle of ${ 30 }^{ o }$ to the normal.

What happens to the light after striking the boundary?

A

It is absorbed at the boundary.

B

All of the light is reflected at the boundary.

C

Some of the light is reflected and some is refracted at the boundary.

D

All of the light is refracted at the boundary.