Question

An object is placed at a distance of 20 cm from a concave lens and its erect image is

formed at a distance of 10 cm from the lens on the same side as the object. Calculate the focal length

of the given lens Also calculate the value of magnification.​

Answer 1

Explanation:

Given , u = 20 cm

v = 10cm

Now f =

1/f = 1/v - 1/u

-1/f = -1/10 + 1/20

-1/f = -1/20

f = 20cm

Now m= v/u

m = 10/20

m = 1/2

Hope it helps...