If the power of a lens is - 4.0 D, then it means that the lens is a 

(A) concave lens of focal length -50 m 

(B) convex lens of focal length +50 cm 

(C) concave lens of focal length -25 cm 

(D) convex lens of focal length -25 m 

 

Answer - 

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Slide2.JPG

So, the correct answer is (c)  

 

 

  1. Class 10
  2. Solutions to CBSE Sample Paper - Science Class 10

Transcript

Question 39 If the power of a lens is โˆ’ 4.0 D, then it means that the lens is a (A) concave lens of focal length โˆ’50 m (B) convex lens of focal length +50 cm (C) concave lens of focal length โˆ’25 cm (D) convex lens of focal length โˆ’25 m Now, Power of lens = ๐Ÿ/๐’‡ Here, focal length is in meter Since Power = โˆ’4D ๐Ÿ/๐’‡ = โˆ’4 (โˆ’1)/๐‘“ = f f = (โˆ’1)/4 m Converting in cm f = (โˆ’1)/4 ร— 100 cm f = โˆ’25 cm Since focal length is negative โˆด it is a concave lens So, the correct answer is (C)

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

About the Author

CA Maninder Singh's photo - Founder at Teachoo
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