Refraction by a transparent spherical surface

[bcjochim07]

Homework Statement

Parallel light rays enter a transparent sphere along a line passing through the center of the sphere. The rays come to a focus on the far surface of the sphere. What is the sphere's index of refraction?

Homework Equations

The Attempt at a Solution

so I used the equation that relates object distances and image distances for spherical surfaces: n1/s + n2/s' = (n2-n1)/R

I am calling the radius of the sphere R

(1.00)/s + n2/2R = (n2-1.00)/R and I think for this case s\rightarrow\infty
so n2/2R = (n2-1)/R
n2 = 2(n2-1)
n2 = 2n2 -2
-n2=-2
so n2= 2.00 Is this correct?

 

[Kurdt]

Looks fine to me.