HC Verma Chapter 18 Problem 67 – Concave lens – object at 2f

Given

u=-30 cm, f=-15 cm concave

Find

Image v

Formula

1/v = 1/f + 1/u

Solution

1/v = 1/(-15) + 1/(-30) = -3/30; v = -10 cm

Answer

v = -10 cm (virtual, erect, diminished)

Diagram / Concept

Concave lens always gives virtual erect diminished image

Notes

m = (-10)/(-30) = +1/3