Question

A ray of light is incident at the glass-water interface at an angle $i$ . If it finally emerges parallel to the surface of the water, then the value of ${\mu }_g$ would be

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

Answer 1

Answer: (B)

Applying, Snell's law $\left(\mu sin\left(i\right)=\text{ constant }\right)$ at $1$ and $2$ , we have

${\mu }_1\sin i_1={\mu }_2\sin i_2$
Here, ${\mu }_1={\mu }_{\text{glass }},i_1=i$
$\therefore {\mu }_2={\mu }_{\text{air }}=1$ and $i_2=90^{\circ }$
$\therefore {\mu }_g\sin (i)=1\times \sin 90^{\circ }$
$\therefore {\mu }_g=\frac{1}{\sin (i)}$