A student's near point is 0.5 m and far point is 3m . What are the powers of the spectacle lenses required for (a) reading the books and (b) seeing the distant objects ?

Options

A. `-2` d and `+3` D
B. `+2` d and `-3` D
C. `+2` d and `-0.33` D
D. `-2` d and `+0.33` D

Answer

C

Explanation

For reading, `mu=-25` cm, `v=-50` cm, f= ?
`(1)/(f)=(1)/(v)-(1)/(u)=-(1)/(50)+(1)/(25)=(1)/(50)`
`P=(100)/(f)=(100)/(50)=+2D`
for seeing distant object,
`f.= "distantance of far point" =-3` m
`P=(1)/(f.)=-(1)/(3)D=-0.33D`