Question

a boy uses spectacle of focal length -50 cm. name the defect he is suffering from. compute the power of his lens.

Answer 1

Because the focal lenth (f=-50cm) is negative, so it is a Diverging Lens.

Thus, the boy is suffering from “Myopia" or “Short Sightedness".

Focal Length (f) = -50cm = -(0.5)m
Now, Power of the lens =>

P = 1/f

P = 1/(-0.5)

P = -2 D....●

So, the power of the lens is -2 Diopter.


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Answer 2

P = 1/f

P = 1/(-0.5)

P = -2 D...

So, the power of the lens is -2 Diopter.

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