Question

An object kept at a distance of 60cm from a lens gives a virtual image at a distance of 20cm over the same side of the lens. what is the focal length of the lens?​

Answer 1

Answer:

30 is correct answer this is right answer

Answer 2

Answer:

Given, u = - 60 cm

v = - 20 cm

By using the lens formula

$\frac{1}{f} = \frac{1}{v} - \frac{1}{u} \\ = \frac{1}{ - 60} - ( \frac{1}{ - 30} ) \\ = \frac{1}{30} - \frac{1}{ 60} \\ = \frac{2 - 1}{60} \\ = \frac{1}{60} \\ = f = 60cm$

Hope this helps mate...