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?




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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Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.