The distance between the crystalline lens and retina of a person is 2.4 cm. Find the normal power of his eye lens system. What will be the power of his lens reading a book 25 cm from the eye?
RajivShastry:
2.654 D ?
I don’t have the answer
How did u get this answer
the normal power of his eye lens system. - 41.67D
How?
I think f = 2.654
So p = 1/f
p = 1/v - 1/u
Answers
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(a) Power = 1/f (in metres)
f = 2.4 cm = 0.024 m
Power = 1/0.024 = +41.66 D
(b) Object distance, u = 25 cm = 0.25 m
Image distance, v = 2.4 cm = 0.024 m
f = uv/(u-v) = 0.25 x 0.024 ( 0.25 - 0.024) = 0.0265
Power = 1/f = 1/0.0265 = +37.73 D
Since our eyes have convex lens, the power is positive
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