Question 39 If the power of a lens is โ 4.0 D, then it means that the lens is a (A) concave lens of focal length โ50 m (B) convex lens of focal length +50 cm (C) concave lens of focal length โ25 cm (D) convex lens of focal length โ25 m Now,
Power of lens = ๐/๐
Here,
focal length is in meter
Since
Power = โ4D
๐/๐ = โ4
(โ1)/๐ = f
f = (โ1)/4 m
Converting in cm
f = (โ1)/4 ร 100 cm
f = โ25 cm
Since focal length is negative
โด it is a concave lens
So, the correct answer is (C)

Solutions - CBSE Class 10 Sample Paper for 2022 Boards - Science [MCQ]

Solutions - CBSE Class 10 Sample Paper for 2022 Boards - Science [MCQ]

About the Author

CA Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 11 years and a teacher from the past 11 years. He teaches Science, Accounts and English at Teachoo