Question

Your aunt just turned 50 and now needs glasses to read.

Answer 1

Answer:

(a) hypermetropia

(b) convex lens

(c) 133.33 cm

(d) - 21.05 cm

Explanation:

(a) As she is old age, so she is suffering from hypermetropia.

(b) It is the defect due to which a person is not able to see the nearby objects clearly, so it is cured by convex lens of suitable focal length.

(c) Power, P = + 0.75 D

Focal length is the reciprocal of power of lens.

f = 1/ P = 1/0.75

f = 133.33 cm

(d) v = -25 cm, f = 133.3 cm

use lens equation

$\frac{1}{f}=\frac{1}{v}-\frac{1}{u}$

$\frac{1}{133.3}=\frac{-1}{25}-\frac{1}{u}$

$\frac{-1}{u}=\frac{133.33+25}{133.33\times25}$

u = - 21.05 cm