Question

An object kept 60 cm from a lens
gives a virtual image 20 cm in front
of the lens? Is it a converging lens or​

Answer 1

From lens formula,

f

1

=

v

1

−

u

1

=

(−20)

1

−

(−60)

1

=−

60

2

⇒f=−30cm

Since the focal length is negative. It is a diverging lens.