Question

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

Answer 1

initially the object distance was 60cm and magnification was given. So we can find the image distance(v) by the formula {m=-u/v}. image distance came out to be 30cm.

now we have to find the object distance(u) when image distance and magnification are given.

using the same formula, we can find out the object distance. Therefore to obtain a magnification of 1/3, the object has to be placed at a distance of 90 cm from the mirror.

Answer 2

we can use unitary method to find this

when magnification is 1/2,distance =60cm
when magnification is 1,distance is=60×1/2cm
when magnification is 1/3,distance is=30cm÷1/3=30×3=90cm

Hence object should be placed at a distance of 90cm to get a magnification of 1/4