Question

We are given a concave lens of focal length 20 cm. Draw a ray diagram to show the nature , position and size of the image formed when the object is kept at a distance of a) 40 cm b) 15 cm

Answer 1

Explanation:

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