Question

Holding a lens 21 c m from a page you see the image of the type as erect and magnified with m = 1.5 . Is the image virtual or real? virtual real What is the focal length of the lens? cm

Answer 1

Magnification is positive hence image is virtual.

Here we have given,

M = 1.5 = - v/u

Here u = 0.21 m

So that v = 0.315 m

So focal length will be given as,

f = v×u/ v-u = 0.315×0.21/0.315- 0.21= 63 cm

Hence focal length f = 63 cm