Question

Find the power of a convex lens if the image formed is at a distance of 10 cm from the lens when the object is placed on the other side of the lens at 40 cm from the optical centre?
A) 12.5 diopters B) 7.5 diopters C) -12.5 diopters D) -7.5 diopters

Answer 1

Answer:

A) 12.5 diopters

Explanation:

u= -40 cm , v= 10 cm

By lens formula, we get

-1/u + 1/v= 1/f

1/40 + 1/10 =1/f

1/f = (4+1)/40 =5/40 =1/8

f =8 cm

So P(power) =100/f(in cm) =100/8 = +12.5 D

Ans. P = +12.5 D

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