A concave mirror is placed inside water its shining surface upwards and principal axis vertical as shown in figure. Rays are incient parallel to the principal axis of the concave mirror. Find the position of the final image.

Explanation

The incident rays will pass undeviated through the water surface and strike the mirror parallel to its principal axis. Therefore for the mirror, object is at `oo`. Its image A (in figure) will be formed at focus which is 20 cm from the mirror. Now for the interface between water and air, d = 10 cm
`:. d'=d/((n_(w)/n_(a)))=10/((4//3)/1)=7.5` cm