Question

what is meant by power of lens write SI unit a student uses a lens of focal 40 cm and another of - 20 cm write the nature power of each lens

Answer 1

hey!!

here is ur answer!!

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The deviation of the incident light rays produced by a lens on refraction through it, is a measure of its power.

The S.I unit of power is dioptre (symbol D)

power of lens = 1/ focal length ( in meter)

when focal length is 40 that mean it is positive so therefore the resulting power will also be positive. If the power is positive it considered as power of convex lens.

power = 1/ 0.4 = 2.5 D

another focal length is -20..

Power = 1/ 0.2 = 5 D

the resulting power will be also negative therefore the resulting power is the power of concave lens...

Hope this helps u!!

Answer 2

I hv explained the answer in a brief manner down with a pic ...

The ability of a lens to converge and diver get light rays depends on its focal length...