A Convex Refracting Surface Has a Radius of 12 Cm

Multiple Choice

A convex refracting surface has a radius of 12 cm.Light is incident in air (n = 1) and refracted into a medium with an index of refraction of 2.Light incident parallel to the central axis is focused at a point:

A) 3 cm from the surface
B) 6 cm from the surface
C) 12 cm from the surface
D) 18 cm from the surface
E) 24 cm from the surface