Question

Where should be an object be placed infront of a concave mirror of focal length 20cm so as to obtain a 2times magnified real image.

Answer 1

Explanation:

m=2

-(v/u)=2

v=2u

according len's formula

1/f=1/v-1/u

1/-20= 1/2u+1/u. (sign convection of concave mirror)

1/-20= 1+2/2u

1/-20=3/2u

2u=-60

u =.-30

object should be between of principle focus & centre of curvature