Question

find the power of concave lens made up of a material of refractive index 1.5 the radius of the curvature of lens 30 and 40 cm respectively...

how's my bio?

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Answer 1

HEY ........

For any convex lens there are two surfaces i.e. left and right

Given -

For right surface R1 = 40cm = 0.4m

For left surface R2 = -40cm = -0.4m

µ = 1.5

f = ?

Solution -

By lens makers formula,

1/f = (µ-1) (1/R1 - 1/R2)

1/f = (1.5-1)(1/0.4 - 1/-0.4)

1/f = 0.5 × (2/0.4)

f = 0.4m = 40 cm

Focal length of lens is 40 cm.

Power = 1/ f =1 /40 ×100 = 2.5 D

Hope I helped...