Q. 304.3( 6 Votes )

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

Answer :

Given,

Focal length of concave lens f = -20 cm

Height of object h_{1}= 5 cm

Image distance v = -15 cm

Object distance u =???

Height of image h_{2} =???

We know that lens formula is:

Substituting the given values in the formula:

u = -60 cm

Substituting the value object height here

Height or size of the image = 1.25 cm

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