Question

far sighted person cannot focus distinctly on objects closer than 1m. What is the power of lens that will permit him to read from a distance of 40 cm?​

Answer 1

Answer:

Explanation:

==>

focal length is given as

1/f = 1/v - 1/u

here

u = -40 cm

v = -100 cm

so,

1/f = (1/-100) - (1/-40)

1/f = (-2+5)/200

1/f = 3/200

or focal length

f = 200/3 cm = 66.67 cm

and power of lens

[here f = 66.67 cm = 0.66m]

P = 1/f = 1/0.66= 1.51 D