A parallel incident beam falls on a solid glass sphere at normal incidenc. Prove that the distance of the fianll image after two refractions is at a distance `(2-mu)//2(mu-1)a` from the outer edge of the sphere. Refractive index of the sphere is `mu` and radius of the sphere is a.

Explanation

To solve the problem, we need to analyze the refraction of light as it passes through a solid glass sphere. We will apply the lens maker's formula and the principles of refraction at spherical surfaces.

### Step-by-Step Solution:

1. **Identify the Parameters:**
- Refractive index of the sphere: \( \mu \)
- Radius of the sphere: \( a \)
- The incident beam is parallel and falls at normal incidence.
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