Find the focal length of a lens of power – 2.0 D. What type of lens is this?




Power of lens = –2.0 D


We know that,

Power of the lens = 1/Focal length

–2 = 1/Focal Length

Focal length = 1/(–2)

Focal length = –0.5 m

Since the focal length is negative, the lens is a concave lens.



  1. Class 10
  2. Chapter 10 Class 10 - Light - Reflection and Refraction (Term 1)

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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