To read a poster on a wall, a person with defective vision needs to stand at a distance of 0.4 m from the poster. A person with normal vision can read the poster from a distance of 2.0m. Which one of the following lens may be used to correct the defective vision?
(a) A concave lens of 0.5 D
(b) A concave lens of 1.0 D
(c) A concave lens of 2.0 D
(d) A convex lens of 2.0 D
Answers
Answered by
33
Given, u = -2m
v = -0.4m
using lens formula
1/f= 1/v-1/u = 1/0.4+1/2 = -5/2+1/2 = -2
As, power , p = l/f = -2D
Power of the lens is negative
So, lens required is a concave lens of 2D
v = -0.4m
using lens formula
1/f= 1/v-1/u = 1/0.4+1/2 = -5/2+1/2 = -2
As, power , p = l/f = -2D
Power of the lens is negative
So, lens required is a concave lens of 2D
Answered by
3
C concave lens of 2.0 D. is the answer
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