Question

An image 2/3rd the size of the object is formed
by a concave mirror at a distance of 20 cm from
it. Find the focal length of the mirror.
​

Answer 1

Answer:

f= -31/20

Step-by-step explanation:

m=-v/u =hi/ho

-v/20=2x/3x

x will be cancelled

v=2/3

so, 1/v+1/u=1/f

u= -20

3/2+i/-20=1/f

3/2-1/20=1/f

f=-31/20