Question

A ray of light travels in the fashion as shown in the figure. After passing through water, the ray grazes along the water-air interface. The value of ${\mu }_g$ in terms of $i$ is

• A. $\frac{1}{\sin i}$
• B. $\frac{3}{\sin i}$
• C. $\frac{2}{\sin i}$
• D. $\frac{4}{\sin i}$

Answer 1

The correct option is A $\frac{1}{\sin i}$

For any pair of media,
$\mu \sin \theta =$ constant


So, from figure,
${\mu }_g\sin i={\mu }_w\sin r={\mu }_a\sin e$
$\Rightarrow {\mu }_g\sin i={\mu }_a\sin e$
$\Rightarrow {\mu }_g\sin i=1\times \sin {90}^{\circ }$
$\Rightarrow {\mu }_g=\frac{1}{\sin i}$
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Why this question? Tips: Identify the number of interfaces at which light is undergoing refraction and apply Snell's law.