Question

A rectangular tank of depth 4m is full of water of refractive index 4/3.when viewed from the top, the bottom of the tank is seen at a depth of

Answer 1

Given:

A rectangular tank of depth 4m is full of water of refractive index 4/3.

To find:

When viewed from the top, the bottom of the tank is seen at a depth of ?

Calculation:

Whenever we watch the bottom of the tank from an angle , the bottom seems to be raised. This depth is known as the apparent depth.

• Light rays from the tank bottom deviate away from the normal at the water-air interface.

• Backward extension of the refracted ray produces a raised image of the bottom , which observers consider as the real bottom.

$\rm \therefore \: apparent \: depth = \dfrac{actual \: depth}{ \mu}$

$\rm \implies \: apparent \: depth = \dfrac{4}{( \frac{4}{3}) }$

$\rm \implies \: apparent \: depth = 3 \: m$

So, the bottom will be observed at an apparent depth of 3 metres.