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Point source of light beneath water.

by Beeza
Tags: beneath, light, point, source, water
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Sep7-06, 03:34 PM
P: 114
A point source of light is 245.0 cm below the surface of a body of water. Find the diameter of the circle at the surface through which light emerges from the water.

Can someone give me a push start as to how to approach this problem? I can't figure it out for the life of me.

I know that v=c/n, and using 1.33 at the index of refraction of water, I can find the velocity of the light as it reaches the surface is 2.3E8m/s. The point source will emit light isotropically in all directions, and I have the distance to the surface... but for the life of me I can't find how to relate this to the diameter of the circle it will leave on the surface.
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Sep7-06, 04:24 PM
berkeman's Avatar
P: 41,017
Does your text cover "total internal reflection"? That's the reason why light that is angled way out to the side won't make it out of the water....
Sep7-06, 04:49 PM
P: 114
Thank You. Im such a bonehead sometimes.

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