Question

A woman can read the large print in a newspaper only when it is at a distance of 56 cm or more from her eyes. (a) Is she nearsighted (myopic) or farsighted (hyperopic), and what kind of lens is used in her glasses to correct her eyesight? (b) What should be the refractive power (in diopters) of her glasses (worn 2.2 cm from the eyes), so she can read the newspaper at a distance of 26 cm from the eyes?

Answer 1

(a) Is she nearsighted (myopic) or farsighted (hyperopic)?

Farsighted

And what kind of lens is used in her glasses to correct her eyesight?

Converging Lens

(b) The refractive power (in diopters) of her glass should be given as :

using equation of motion, we have

1 / d₀ + 1 / d_i = 1 / f

1 / [(26 - 2.2) cm] + 1 / - [(56 - 2.2) cm] = 1 / f

1 / (23.8 cm) - 1 / (53.8 cm) = 1 / f

f = 42.6 cm

We know that, P (in diopters) = 1 / f (in m)

P = 1 / (0.426 m)

P = 2.34 diopters