Question

When the focal length is equal to -15cm, the lens is

Answer 1

Explanation:

Given: f=−15

            v=−10

From mirror formula, v1−u1=f1

                                    −101−u1=−151

                                    u1=151−101

                                    u=−30 cm

Answer 2

Answer:

concave lens is the focal length equal to 15 cm