Question

The optical prescription for a pair of spectacles is, Right eye : +2.50 D
and left eye: +4.00 D. Which of the following statements is true for
above condition ?
a) The lens of left eye has greater focal length
b) The given values are power of concave lenses.
e) The lens of right eye has greater focal length
d) The person is suffering from nearsightedness​

Answer 1

Explanation:

(i) These lenses have negative powers, means the person is nearsighted. Hence he has Myopia eye defect.

(ii) As the lenses have negative powers, so the focal length is negative. Hence they are concave in nature. And concave lenses are thinner in the middle

(iii) We know,

Power of lens, P=

f

1

As power and focal length are inversely proportional to each other, so the lens with lower power will have greater focal length. That is right eye lens, -3.5D lens have greater focal length.