Question

define power of a lens what is its unit? One student use a lens of focal length 50 and another of - 50 cm .what is the nature of the lens and its power used by each of the them​

Answer 1

Power of a lens is the measure of deviation produced by it on incident light.

Its unit is Dioptre(D).

P = 1 /  f(in m)

P = 100 / f ( in cm)

f = 50 cm

Power = 2D

Lens - Convex

f = - 50cm

Power = -2D

Lens - Concave

Answer 2

dioptre is the unit of Power

it is defined as the ability of lend to converge ray of light falling on it

it also define as the reciprocal of focus

methmatically

p=1/f

now numerical

concave lens

convax lens

p=1/50=0.02D

p=-1/50=-0.02D