CBSE Class 10 Science Question 5 of 16

The Human Eye and the Colourful World — Question 5

Back to all questions
5
Question

Question 5

A person needs a lens of power –5.5 dioptres for correcting his distant vision. For correcting his near vision he needs a lens of power +1.5 dioptre. What is the focal length of the lens required for correcting (i) distant vision, and (ii) near vision?

Answer

Power is reciprocal of focal length.

(i) Focal length of the lens required for correcting distant vision = 15.5-\dfrac{1}{5.5} = -0.181 m = -18.1 cm

(ii) Focal length of the lens required for correcting near vision = 11.5\dfrac{1}{1.5} = 0.667m = 66.7cm