A person suffering from presbyopia needs bifocal lens. If he needs two lens of power – 4.0 dioptre and + 2.0…
A person suffering from presbyopia needs bifocal lens. If he needs two lens of power – 4.0 dioptre and + 2.0 dioptre, which one of these two lenses is for the correction of distant vision and what is its focal length ?
Solution
For distant vision: lens of power – 4.0 dioptre
f(meter) = $\dfrac{1}{P}$ = 1/(-4.0D) = -0.25 m or -25 cm