A thin glass (refractive index `1.5`) lens has optical power of `-8D` in air, its optical power in a liquid medium with refractive index `1.6` will be

Options

A. `1` D
B. `-1` D
C. `25` D
D. `-25` D

Answer

A

Explanation

In air `impliesP=(1)/(f.)=((mu_(g))/(mu_(l))-1)((1)/(R_(1))-(1)/(R_(2)))`
In medium, `impliesP.=(1)/(f.)=((mu_(g))/(mu_(l))-1)((1)/(R_(1))-(1)/(R_(2)))`
`(P.)/(P)=(((mu_(g))/(mu_(l))-1))/(((mu_(g))/(mu_(a))-1))=(((1.5)/(1.6)-1))/(((1.5)/(1)-1))=((-0.1//1.6))/(0.5)`
`P.=-(1xx2)/(16xx1)P=-(1)/(8)(-8D)=1D`