Question

Farsighted woman has a near point of 1.5 m. calculate the focal length of the lenses for her
eye glasses so that she can read a book held at 25 cm. also find power of the lens.
1) f = + 20 cm and p = + 4.4 d 2) f = + 10 cm and p = + 5.4 d
3) f = + 30 cm and p = + 3.3 d 4) f = + 10 cm and p = + 2.3 d

Answer 1

Answer:

c) f=+30 p=+3.3

Explanation:

u=-25 cm

v=-1.5 m (near-point of women)

= -150 cm

1/f= 1/v - 1/u = 1/-150 + 1/25 = 5/150

f=+30cm

p=1/f(in meters) = 1/0.3 = 3.33 d