CBSE Class 10 Sample Paper Science Solution - For 2023 Boards

A lens of focal length 5 cm is being used by Debashree in the laboratory as a magnifying glass. Her least distance of distinct vision is 25 cm.

  1. What is the magnification obtained by using the glass?
  2. She keeps a book at a distance 10 cm from her eyes and tries to read. She is unable to read. What is the reason for this?



  • Focal length of given lens, f = +5cm (given)
  • The person’s least distance of distinct vision is 25cm
  • This means the image will be formed at 25cm from the lens. 
  • Since she does not require a screen to view this object, it is a virtual image and is formed on the same side as the object
  • Thus, v=-25cm
  • Magnification, m = v/u

Question 31 - A lens of focal length 5 cm  - teachoo.jpg


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CA Maninder Singh is a Chartered Accountant for the past 14 years and a teacher from the past 18 years. He teaches Science, Economics, Accounting and English at Teachoo