A person needs a lens of power –0.5 dioptre for correcting his distant vision he needs a lens of power +1.5…
A person needs a lens of power –0.5 dioptre for correcting his distant vision he needs a lens of power +1.5 dioptre for correcting his near vision. What is the focal length of the lens required for correcting his
(i) distant vision, (ii) near vision?
Solution
(i) For correcting his distant vision, $P = -0.5\ \text{D}$
$f = \dfrac{1}{P} = \dfrac{1}{-0.5} = -2.0\ \text{m}$
(ii) For correcting his near vision, $P = +1.5\ \text{D}$
$f = \dfrac{1}{P} = \dfrac{1}{+1.5} = +0.67\ \text{m}$