Question

When an object is placed at a distance of 60cm from a convex mirror the magnification produced is 1/2. Where should the objects be placed to get a magnification of 1/3

Answer 1

Given:
u=-60cm
m=1/2
m=-v/u
1/2=-v/-60
-v=-30cm
v=30cm
f=?
by mirror formula:
-1/60+1/30=1/f
on solving:
f=60cm
m=1/3
1/3=-v/u
v=(1/3)u
f=60cm
using mirror formula:
1/u+1/v=1/f
1/u-3/u=1/60
u=-120cm

Answer 2

Answer:

Explanation:

Given :-

u = - 60 cm

m = + 1/2

Solution :-

m = - (v/u) = - 1/2

1/2 = - v/- 60

v = 30 cm.

Using Mirror formula,

⇒ 1/f = 1/u + 1/v = 1/60

⇒ f = 60 cm

Now, m = 1/3

⇒ 1/u + 1/v = 1/f

⇒ 1/- 3 + 1/v = 1/60

⇒ u = - 120 cm

Hence, the objects be placed at 120 cm to get a magnification of 1/3.