Question

To a bird in air, a fish in water appears to be at 30 cm from the surface. If refractive index of water with respect to air is $\frac {4}{3}$ ,the real distance of bird from the surface is

• A. 30 cm
• B. 50 cm
• C. 40 cm
• D. 60 cm

Answer 1

Answer: (C)

40 cm

Answer 2

Snell's law:
n = $\frac {d}{d'}$
In this case, the refractive index of water with respect to air is given as $\frac {4}{3}$. We are given that the fish appears to be at a depth of 30 cm from the surface (d'). We need to find the real depth (d) of the bird.
Applying Snell's law:
$\frac {4}{3}$ = $\frac {d}{30}$
d = $\frac {4}{3}$ x 30
d = 40 cm
Therefore, the correct answer is (C) 40 cm.