Question

a concave lens of focal length 20cm forms and image at the distance of 10cm from the lens what is the distance of the object from the lens​

Answer 1

Answer:

Given f = - 20 cm, (sign convention) , v = - 10 cm

(∴ image formed by concave lens is virtual)

By using lens formula,

or u = - 20

Thus the object is placed at 20 cm from the concave lens