Question

A ray of light is incident at the glass-water interface at an angle \( i \), it emerges finally parallel to the surface of water, then the value of \( \mu_g \) would be: 

• A. \( \frac{4}{3} \sin i \)
• B. \( \frac{1}{\sin i} \)
• C. \( \frac{4}{3} \)
• D. 1

Hint:

At the critical angle, the refracted angle is \( 90^\circ \), and Snell’s law gives the refractive index.

Answer 1

The Correct Option is B

Step 1: Refraction at the interface.
When light emerges from the water surface parallel to the surface, the angle of incidence \( i \) must satisfy the critical angle condition, where the refracted angle is \( 90^\circ \). Using Snell's law: \[ \mu_g = \frac{1}{\sin i} \] Thus, the correct answer is (2).