Question

an object is placed 25 cm from a plane mirror the mirror is moved by 5 cm towards the object find the distance between the first and second image seen in the mirror

Answer 1

Answer:

Answer is 50 cm

Case-1:

1/f =1/v1 + 1/25 - Eq 1

Case2:

1/f =1/v2 + 1/20 - Eq 2

Eq1 - Eq2

We will get 1/v1 -1/v2 = 1/20 - 1/25

v2-v1/v1v2 =1/100

100(v2-v1) =v1v2

This is satisfied when v2 is 100 and v1 is 50