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_(2)ltf`
B. `f_(1)gt f and f_(2)" becomes negative"`
C. `f_(2) gt f 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))-1)((2)/(R ))`
for, `mu_(L_(1))=(4)/(3), f_(1)=4R`
for, `mu_(L_(2))=(5)/(3), f_(2)=-5R rArr f_(2)=(-)ve`