Focal length of a convex lense in air is `10cm`. Find its focal
length in water. Given that `mu_g=3//2` and `mu_w=4//3`.

Options

A. 2.5 cm
B. 5 cm
C. 20 cm
D. 40 cm

Answer

D

Explanation

`(1)/(f_1)=(._amu_g-1)((1)/(R_1)-(1)/(R_2))` …(i)
`(1)/(f_(omega))=(._(omega)mu_g-1)((1)/(R_1)-(1)/(R_2))` ….(ii)
`f_(omega)/(f_(a))=((._amu_(g)-1))/((._omegamu_(g)-1))=((._amu_(g)-1))/(((._amu_(g))/(._amu_omega)-1))`
`(f_(omega))/(10)=(((3)/(2)-1))/(((3//2)/(4//3)-1))=4impliesf_(omega)=40cm`