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CBSE Class 10 Science Question 39 of 60

Solved 2022 Term 1 Question Paper CBSE Class 10 Science — Question 15

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Question

Question 39

If a lens can converge the sun rays at a point 20 cm away from its optical centre, the power of this lens is –

  1. +2D
  2. –2D
  3. +5D
  4. –5D
Answer

+5D

Reason — Given,

Convex lens as converging rays.

Focal length (f) = 20 cm

P = 100f(cm)\dfrac{100}{\text{f(cm)}}

Substituting we get,

P = 10020\dfrac{100}{20} = +5D [positive sign as convex lens.]