A thin convergent glass lens `(mu_g=1.5)` has a power of `+5.0D.` When this lens is immersed in a liquid of refractive index `mu_1,` it acts as a divergent lens of focal length `100 cm.` The value of `mu_1` is

Options

A. `5//3`
B. `4//3`
C. `sqrt(3)`
D. `5//4`

Answer

1

Explanation

By using `f_(1)/f_(a) = (""_(a)mu_(g)-1)/(""_(l)mu_(g)-1)` where `""_(l)mu_(g)= mu_(g)/mu_(l) =1.5/mu_(1)` and `f_(a)=1/P =1/5 20cm implies (-100)/20 =(1.5-1)/(1.5/mu_(1) -1) implies 5//3`