Question

A bright point source of light is under water at a depth 12 cm. An observer's eye is at a height 12 cm above the surface of water. The distance of the image of the point source from the eye of the observer is (take refractive index of water as 4/3)

• A. 21cm
• B. 9cm
• C. 28cm
• D. 16cm

Answer 1

The correct option is A 21cm

Solution

The distance of image from observer

=observer's height + apparent depth

We know,

$\frac{apparentdepth}{realdepth}=\frac{1}{\mu }$

Here, $A.D=\left(\frac{3}{4}\right)$ R.D.

$AD=\frac{3}{4}\times 12=9cm$

So, Image distance = 12cm + 9cm

= 21 cm

option A is correct.