Question

Wwhat is mean by the power of lens ?A student use a lens of focal length 40cm and other of 20cm .Write the nature and power of lens ?

Answer 1

power of lenses means the amount of deviation produced by a lenses. the power of 20cm lenses will me

Answer 2

the power of a lens is a measure of the degree of convergence or divergence of light rays falling on it. the unit of the power of lens is diopter
P=1/f
in first case
f=40cm=0.4m
p=I/f
p=1/0.4
p=10/4
p=2.5D
power of lens is positive mean it is convex lens

in second case
f=20cm
f=0.2m
p=1/f
p=1/0.2
p=10/2
p=5D
power of lens is positive mean it is convex lens


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