A glass lens of refractive index 1.45 disappears when immersed in a liquid. What is the value of refractive index of the liquid ?
Answers
Refractive index means ratio of speed of light in vacuum and speed of light in any medium. here glass lens will be disappears when we immersed the lens into a liquid . It means speed of light through lens for air medium is same as speed of light through lens for liquid medium. e.g., refractive index of lens with respect to medium = 1 . or you can say that refractive index of lens = refractive index of liquid .
That's why refractive index of liquid = 1.45
In another way,
as you know, formula for focal length of any lens
here, μ is refractive index of lens with respect to medium
e.g.,
when lens is disappears means power of lens goes to zero.
so, P = 1/f = 0 , f = ∞
it means μ = 1 [ here , we assume ( 1/R₁ - 1/R₂) ≠ 0 ]
hence, refractive index of lens = refractive index of medium = 1.45