A man uses a concave mirror for shaving. He keeps his face at a distance of 25 cm from the mirror and gets an image which is 1.4 times enlarged. Find the focal length of the mirror.

87.5 cm

The distance of the man’s face from the mirror,

u =25cm

The magnification in the image= 1.4

Using the mirror formula

Then, f= -87.5cm

Hence, the focal length of the concave mirror is 87.5cm