Question

The power of combination of two lenses is +3 D. If the focal length of a convex lense is 20 cm.then find out the nature, power and focal length of outer lense

Answer 1

Answer:

Convex lens, 7.7D,13cm.

Explanation:

The power of combination of two lenses is +3 D.

Focal length of convex lens is 20 cm.

Focal length of the combination is

F=1/p

=1/3

=0.33m

=33cm

Focal length of other lens

=Focal length of combination-Focal length of convex lens

=33-20

=13cm

Power of this lens

=1/f

=1/13cm

=1/0.13m

=7.7D

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