Prove that the limiting angle of incidence of a ray that can be transmitted by an equilateral prism of `mu = sqrt(7//3)` will be `30^@`.

Explanation

To prove that the limiting angle of incidence of a ray that can be transmitted by an equilateral prism with a refractive index \( \mu = \sqrt{\frac{7}{3}} \) is \( 30^\circ \), we will follow these steps:

### Step 1: Understand the Geometry of the Prism
An equilateral prism has all angles equal to \( 60^\circ \). When light enters the prism, it refracts at the first face and then exits through the second face. We denote the angle of incidence at the first face as \( I \), the angle of refraction at the first face as \( R_1 \), and the angle of refraction at the second face as \( R_2 \).

### Step 2: Apply Snell's Law
At the first interface (air to prism), Snell's law states:
\[
...