Question

A person needs a lens of power +3D for correcting his near vision and –3D for correcting his distant vision. Calculate the focal lengths of the lenses required to correct these defects.

Answer 1

P = `1/f`

P₁ = +3D

= `1/f_1`

F₁ = `1/3`m

= + 0.33 m (Convex lens)

P₂ = –3D

= `1/f_2`

F₂ = `-1/3`m

= –0.33 m (Concave lens)