Home » Problems » A numerical Problem from optics


A numerical Problem from optics

AK asks:

When an object is kept at a distance of 60cm from a concave mirror, the magnification is 1/2. Where should the object be placed to get magnification of 1/3??

please answer this question….


In the first part, u=-60, m=(-)1/2 implies v=-30 cm (Since the image must be real as concave lens form virtual image of bigger size only)

Substituting in eqn mirror_formula

or  mirrorformula

we get f = –20 cm

In II case




substituting in mirrorformula

we get u=4f=4 x (-20)=-80 cm

(If this is not the expected answer please respond)

1 Comment

  1. electricity question,
    Q.1- A heating element of a hot plate on an electric cooking range draws 12 amperes from 240 V mains. How many kwh of energy will be consumed in one hour and 15 minutes
    (A) 1.2
    (B) 3.2
    (C) 6.0
    (D) 7.2

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: