Question

A bird is flying at a height 24 cm above the free surface of water. At what distance will a fish, which is 6 cm below the free surface of water, see the bird ?

• A. 8 cm
• B. 24 cm
• C. 32 cm
• D. 38 cm

Answer 1

The correct option is D 38 cm

Lets first find the image of the bird formed due to refraction by water surface.
For this
Given,
Object distance (u) = 24 cm
Radius of curvature = Infinity
So the curved surface formula will become

$\frac{n_2}{v}=\frac{n_1}{u}$
Putting given values

$\frac{4/3}{v}=\frac{1}{24}$

Which gives

v = 32 cm

As fish itself is at a depth 6 cm from the free surface of water, so distance at which fish will sew bird is,
D = 32 + 6 = 38 cm