Question

the near point of hypermetropic eye is 50 cm. calculate the power of the lens to enable him to read a book at 40 cm​

Answer 1

Answer:

Power of the lens is +2d.

Explanation:

v = -40

u = -50

1/f = 1/v - 1/u

= (1/-40) - (1/-50)

= (-5 - (-4))/200

= (-5 + 4)/200

= -1/200

f = -200

d = -f/100

= - (-200)/100

= 200/100

= 2

Answer 2

Answer:

0.5D

Explanation:

N= 50cm

N'= 40cm

f=NN'/N-N'

=50x40/50-40

=2000/10

=200cm

p=100/f

=100/200

=1/2

=0.5D