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….

Ans:

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

or

we get f = –20 cm

In II case

m=-1/3

v=u/3

f=-20cm

substituting in

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

**(If this is not the expected answer please respond)**

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