angle of refraction through ice into water

[goWlfpack]

1. The problem statement, all variables and given/known data

A layer of ice having parallel sides floats on water. If light is incident on the upper surface of the ice at an angle of incidence of 15.0°, what is the angle of refraction in the water?

2. Relevant equations



3. The attempt at a solution
i know its not so simple that i can just use Sin theta n1 = sin theta n2.... but i dont know how the fact that it is parallel will change the equation. Should i find the angle of refraction in the ice and then use that as the angle of incidence for the water???

[mgb_phys]

The equation only applies at a point on the surface - being parallel just means that you don't care where on the surface.

It's almost the same as the typical experiment with light going through a glass block.
You simply apply Snell's law ( n1 sin t1 = n2 sin t2 ) at each surface.
You will need the refractive index of ice and remember which way light bends at each surface.

[G01]

Should i find the angle of refraction in the ice and then use that as the angle of incidence for the water???

Yup. That's how you should go about this problem. Use Snell's law twice, once at each interface.