Finding light speed in a material given incident and refracted angles

[jsalapide]

Light strikes the surface of a transparent material at an angle of incidence of 30. If the refracted angle in the transparent material is 20, what is the speed of light in the material?

Is it possible to solve this problem without their index of refraction?
If possible, how?

 

[Doc Al]

Use Snell's law.

 

[jsalapide]

I've used it before, but the index of refraction is not given. Should I assume that the index of both material are equal?

 

[Doc Al]

I've used it before, but the index of refraction is not given.

But the angles are given.

Should I assume that the index of both material are equal?

If the indices were equal, could the angles be different? One thing I would assume is that the light striking the material starts out in air/vacuum.