# A concave lens has focal length of 20 cm. At what distance from the lens can a 5 cm tall object be placed so that it forms an image at 15 cm from the lens? Also calculate the size of the image formed.

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Object - distancee= u=?

Image distance=v=15cm

object height ==5cm

Image height==?

1/f=1/v-1/u

1/u=1/v-1/f

1/u=1/15-1/20

1/u=4-3/60

1/u=1/60

u=60cm

Therefore the object must be placed at a distance of 60cm from the lens

v/u=

=15/60*5=5/4=1.25cm