Question
Mon February 18, 2013 By:

A convex mirror produces a magnification of 1/2 when an object is placed at distance of 60cm from it. Where should the object be placed so that the size of the image becomes 1/3 of that of the object?

Expert Reply
Mon February 18, 2013
In case of convex mirror,

In the first part, u=-60cm ,

m=1/2 implies v=30 cm (Since the image must bevirtual)

onlSubstituting in eqn 

or  

we get f = 60 cm

In II case

m=1/3=0.33

m=-(v/u)

v=-u/3

f=60cm

substituting in 

we get u=-2f=(-2)x 60cm =-120cm

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