Question

A glass prism is immersed in water as shown in the figure. When a beam of light incident is incident normally on the face $ab$ , it is internally reflected at the face $ad$ . If the refractive index of glass is $1.5$ and that of water is $4/3$ , then

• A. $sin\theta < \left(\right.2/3\left.\right)$
• B. $sin\theta >\left(\right.8/9\left.\right)$
• C. $\left(\right.2/3\left.\right) < sin\theta < \left(\right.8/9\left.\right)$
• D. None of these

Answer 1

Answer: (B)

$\theta >\theta _{C}$ , where $\theta _{C}$ represents the critical angle for the pair of media
$sin\theta >sin\theta _{C}$
$sin\theta _{C}=\frac{\mu _{rarer}}{\mu _{denser}}=\frac{4/3}{3/2}=\frac{8}{9}$
$sin\theta >\frac{8}{9}$