Question

The defective eye of a person has near point 0.5m and point 3m. The power far corrective lens required for (i) reading purpose and (ii) seeing distant objects, respectively are:
(a) 0.5D and +3D
(b) +2D and -1/3D
(c) -2D and +1/3D
(d) 0.5D and -3.0D

Answer 1

answer : option (B) +2D and -1/3 D

(1) reading purpose,

v = -50cm , u = -D = -25 cm [ for human eyes ]

now applying lens maker formula,

1/f = 1/v - 1/u

= 1/-50 - 1/-25

= 1/-50 + 1/25

= 1/50

f = 50cm

so, power of lens is P = 100/f = 100/50 = +2D [ here D is dioptre ]

(2) seeing distinct objects,

u = ∞ , v = -3m = -300cm

using lens maker formula,

1/f = 1/-300 - 1/∞

= -1/300

f = -300

so, power of lens is P' = 100/-300 = -1/3 D

also read similar questions : The far point of a near sighted person is 00cm in front of eye. What is the nature and power of the lens required to ena...

https://brainly.in/question/31085

the near point of a hypermetropic eye is 1m. what is the power of the lens required to correct his defect? Assume that t...

https://brainly.in/question/2007585

Answer 2

$\huge\bold\purple{Answer:-}$

(b) +2D and -1/3D