NCERT Question 17 - Chapter 10 Class 10 - Light - Reflection and Refraction

Last updated at August 17, 2026 by

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A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?

 

Answer

Given

Power of lens = +1.5 D

 

We know that,

Power of the lens = 1/Focal length

1.5 = 1/Focal Length

Focal length = 1/1.5

Focal length = 10/15

Focal length = 2/3

Focal length = +0.67 m

 

Since the focal length is positive, the lens is a convex lens.

And convex lens are converging lens

 

Hence, the prescribed lens is converging.

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