Question

A long-sighted person cannot see objects nearer to his eye less than 50 cm. To enable him to read a book 25 cm away, he should use
spectacle lenses whose power in dioptres is​

Answer 1

Answer:

Power of the lens is-0.5d.

Explanation:

v = -50

u = -25

1/f = 1/v - 1/u

= (1/-50) - (1/-25)

= (-1 - (-2))/50

= (-1 + 2)/50

= 1/50

f = 50

d = -f/100

= -(50)/100

= -50/100

= -1/2

= -0.5