A thin convex lens made from crown glass `(mu=(3)/(2))` has focal length f. When it is measured in two different liquids having refractive indices `(4)/(3)` and `(5)/(3)`, it has the focal lengths `f_1` and `f_2` respectively . The correct relation between the focal lengths is ,

Options

A. `f_1=f_2ltf`
B. `f_1gtf` and `f_2` becomes negative
C. `f_2gtf` and `f_1` becomes negative
D. `f_1` and `f_2` both become negative

Answer

B

Explanation

By lens maker's formula for convex lens
`(1)/(f)=((mu)/(mu_L))((2)/(R))`
for, `mu_(L1)=(4)/(3)`,`f_1=4R`
for `mu_(L2)=(5)/(3)`,`f_2=-5R`
`impliesf_2=(-)ve`