Question

If the far point of eye lens is 10 M find power of the lens required to correct this defect

Answer 1

f = Focal length of eye, y = shifted far point, P = power of lens required.
Now,
1/f = 1/25 - 1/y
convert into meter 
1/f = 4 - 1/10
1/f = (40 - 1)/10
1/f = 39/10
1/f = P = 3.9 Dioptre. ANSWER.
thanks...

Answer 2

Answer:

0.1 D

Explanation:

Here, far point < ∞

Hence, the individual suffers from myopia.

Let us take u = -∞

v  = -10m

By lens formula,

1/f = 1/v - 1/u

1/f = -1/10 + 1/∞

Since ∞ = 1/0, 1/∞ = 0

Hence, 1/f = -1/10

We know that P = 1/f

So, P = -1/10 = -0.1D