Internal Reflections in a Sphere. A ray of light PQ (Fig. 1) incident at any point Q on the surface of a transparent sphere is partly reflected and partly refracted along QR1. At R1 it is partly reflected along R1R2, and partly emerges along R1s1. The same thing occurs at R2, R3, etc. on which the successive reflected portions fall. AB is the diameter parallel to the incident light, and OQ the radius to the point of incidence. Let μ denote the index of refraction of the material of the sphere relative to the surrounding medium. Divide OA in C so that OC : OA = 1 :μ