Question

refractive index of convex lens material is 1.46.the refractive index of Benzene and water are 1.5 and 1.0 respectively
how does the lens behave when it is kept in Benzene and water.
answer it fast pls
I will definitely mark ur answer as the brainliest

Answer 1

we know, focal length formula is given by
$\frac{1}{f}=(\mu-1)[1/R_1-1/R_2] - - - (1)$
here μ is relative refractive index of lens .means refractive index of lens with respect to medium.

you also know, convex lens is converging lens because focal length of convex lens is positive.so, power of lens will be positive.

now, when lens is placed in Benzene of refractive index 1.50
then, relative refractive index of lens,μ = refractive index of lens/refractive index of benzene = 1.46/1.150
e.g., μ = 1.46/1.50 < 1
(μ - 1 )< 0 ,from equation (1) it is clear that 1/f < 0 when (μ - 1 )< 0 , hence , focal length will be negative.
so, power will be negative . hence, lens will be diverging in benzene liquid.

now, if lens is immersed in water then , relative refractive index of lens = 1.50/1 > 1 , focal length positive. so, power of lens will be positive.
and hence, nature of lens unchange . e.g., converging.