Point source of light beneath water.

AI Thread Summary
To determine the diameter of the circle at the water's surface where light emerges from a point source located 245.0 cm below, one must consider the principles of refraction and total internal reflection. The index of refraction for water is 1.33, which affects the angle at which light can exit the water. Light emitted isotropically from the source will create a cone of light, and only the light rays that strike the water's surface at angles less than the critical angle will emerge. The critical angle can be calculated using Snell's Law, and from this, the radius of the circle can be derived. Ultimately, the diameter of the circle can be found by doubling the radius determined from the critical angle calculations.
Beeza
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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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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...
 
Thank You. I am such a bonehead sometimes.
 
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