A Slab of Material 1 Rests on the Surface of a Slab

Multiple Choice

A slab of material 1 rests on the surface of a slab of material 2.A light ray in material 1 has an angle of incidence of 30° on the interface between the materials,while the ray in material 2 has an angle of refraction of 45°.What is the critical angle of incidence for total internal reflection for a ray of light going from material 2 to material 1?

A) 30°
B) 45°
C) In this case there is no critical angle.
D) At least one of the indices of refraction or its equivalent is needed to solve this problem.