Consider the situation shown in figure. Water $\left(\mu_w=\frac{4}{3}\right)$ is filled in a breaker upto a height of 10cm. A plane mirror is fixed at a height of 5cm from the surface of water. Distance of the image of an object O at the bottom of the beaker formed by the mirror after reflection from it is

12.5 cm

$D_{\text {apparent }}=\frac{D_{\text {actual }}}{\mu_{\text {rel }}}=\frac{10}{\frac{4}{3}}$ = 7.5 cm

So, the object appears to be raised by 10 cm − 7.5 cm = 2.5 cm

Hence, distance between mirror and O' = 5 + 7.5 = 12.5 cm

So, final image will be formed at 12.5 cm behind the plane mirror.