Question

size of the image of an object by a concave lens of focal length 20 cm is observed to be reduced to 1/3rd of its size find the distance of the object from the lens

Answer 1

★Hello Vicky★

Check out attachment which I provide u

Answer 2

As it is a concave lens image would be virtual so magnification is only positive

»m=1/3

»v/u=1/3

»u=3v

We know that

1/v-1/u=1/f

1/v-1/3v=1/-20

3/3v-1/3v=1/-20

2/3v=1/-20

V=-40/3 cm

3V=U

U=-40 cm

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