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## Homework Statement

A light ray falls from the air (##n_a=1##) into the center of the upper surface of a long cilindrical glass tube with an index of refraction ##n_t=3/2##. The tube is submerged into water all the way to the upper edge and the waters index of refraction is ##n_w=4/3##. What is the maximum entry angle of the light ray at which it will only be traveling inside the glass?

a)##arcsine(1/6)##

b)##arcsin(\sqrt{15}/6)##

c)##arcsin(\sqrt{17}/6)##

## Homework Equations

3. The Attempt at a Solution

I gues the snells law must be used ##n_1sin(x_1)=n_2sin(x_2)## but i don't get the problem. What is meant by maximum entry angle at which the beam will be traveling inside the cylinder only and how do i get that? I don't know my starting points. Could you hint?[/B]