Question

3. At what distance from the face of a person, a
shaving mirror of focal length 15 cm should be
placed, so as to obtain an erect image of face 3
times magnified?​

Answer 1

Answer:

Focal length ,F = ?

object distance is = -20cm

Magnification ,1.5=−20−V

V=30cm

using the mirror formula 

V1+u1=F1

301−201=F1

602−3=F1=F=−60cm