A light ray strikes a hexagonal ice crystal floating in the air at a 30° angle to one face, as shown below. The hexagonal faces of the crystal are perpendicular to the plane of the page. All the rays shown are in the plane of the page, and nice = 1.30. Which outgoing ray is the correct one?
A)A
B)B
C)C
D)D

Question

A light ray strikes a hexagonal ice crystal floating in the air at a 30° angle to one face, as shown below. The hexagonal faces of the crystal are perpendicular to the plane of the page. All the rays shown are in the plane of the page, and nice = 1.30. Which outgoing ray is the correct one? 
A)A 
B)B 
C)C 
D)D

Quizplus · Accepted Answer

The hexagonal ice crystal is a birefringent material, meaning it splits the incident light into two polarized components with different refractive indices. The ray that enters the crystal at a 30° angle to one face is split into an ordinary ray and an extraordinary ray. In this case, the ordinary ray travels perpendicular to the plane of the page and passes straight through the crystal without bending or changing direction. The extraordinary ray, on the other hand, is refracted at the surface of the crystal and bent towards the normal (the line perpendicular to the surface). Since the angle of incidence is greater than the critical angle for total internal reflection, the extraordinary ray undergoes total internal reflection twice before exiting the crystal at angle of 30° to the opposite face. This is the ray labeled as option B.

A Light Ray Strikes a Hexagonal Ice Crystal Floating in the Air