Question

an object kept 60 cm from a lens gives a virtual image 20 cm in front of the lens .what is the focal length of the lens ? is it a converging lens or diverging​

Answer 1

Answer:

15cm,converging lens

Explanation:

Here u=-60cm and v=20cm( by sign convention)

By lens equation

1/f=-1/u+1/v

1/f=-(-1/60)+1/20

1/f=1/60+1/20

1/f=(1+3)/60

f=60/4

f=15cm

It is converging lens

Answer 2

Hey ...!!!

Given,

Object distance, u = - 60 cm

image distance, v = - 20 cm

Focal length, f = ?

Now, using the lens formula,

1/f = 1/v - 1/u

= 1/(-20) - 1/ (-60)

= 1/60 - 1/20

= 1 - 3 / 60

= - 2/ 60

i.e., focal length, f = - 30 cm

Hence, the lens is a diverging less with focal length of 30 cm.