Question

An object kept 60 cm from a lens give a virtual image 20 cm in front of the lens. What is focal length of the lens? It is a converging lens or diverging lens.

Answer 1

the focal length is 25 cm and it is converging lens i.e convex lens !! for calculations refer to above pic !!
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hope it helps
#ESHITA

Answer 2

Answer :- - 30cm, lens is diverging or concave

Explanation :

Given :

Object distance, u = - 60cm

Image distance, v = - 20cm

Using lens formula,

1/v - 1/u = 1/f

= 1/f = 1/-20 - 1/-60 = 1/-30

Since, the focal length is negative, the lens is a diverging lens or a concave lens.