Question

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 (ii) near vision.?

Answer 1

As we know ;

focal length = 1/ Power of lens

therefore ;

(1) for distant vision

=> f = 1/ (-5.5)

=> f = 0.18 units

(2). for near vision

=> f = 1/1.5

=> f = 2 units