Question

Prove geometrically that the image formed by a plane mirror is at the same distance behind the mirror as the objects in front of the mirror.

Answer 1

As focal length of plane mirror tends to infinity.
thus,1/f=0
then,1/f=1/u+1/v
0=1/u+1/v
1/u=-1/v
u=-v
hence,the image formed by a plane mirror is at the same distance behind the mirror as the objects in front of the mirror.

Answer 2

Answer:

As focal length of plane mirror tends to infinity . Hence, the image formed by a plane mirror is at the same distance behind the mirror as the objects in front of the mirror