Question

A ray of light is incident on the interface between water and glass at an angle i and refracted parallel to the water surface, then value of ${\mu }_g$, refractive index of glass will be:

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

Answer 1

Answer: (B)

$\frac{1}{\sin i}$

Applying Snell's Law at glass-water interface,

${\mu }_g\sin i=\frac{4}{3}\sin r$

Applying Snell's Law at water-air surface,

The angle of refraction at glass-water interface will be same as angle of incidence at air-water interface.

$\frac{4}{3}\sin r=1\sin {90}^{\circ }=1$

$⟹{\mu }_g\sin i=1$

$⟹{\mu }_g=\frac{1}{\sin i}$