A glass slab of thickness `4 cm` contains the same number of waves as `5 cm` of water, when both are traversed by the same monochromatic light. If the refractive index of water is `4//3,` then refractive index of glass is

Options

A. 43955
B. `1.5`
C. 43954
D. 16/15

Answer

C

Explanation

No. of waves `= ("Thickness of medium")/("Wavelength")`
Given that same number of waves for glass and water
i.e., `(4)/(lambda_(g)) = (5)/(lambda_(w)) :. (lambda_(g))/(lambda_(w)) = (4)/(5)`
`mu_(w) = (lambda_(a))/(lambda_(w))` & `mu_(g) = (lambda_(a))/(lambda_(g)) :. (mu_(g))/(mu_(w)) = (lambda_(w))/(lambda_(g))`
Thus, `mu_(g) = (lambda_(w))/(lambda_(g)) mu_(w) = (5)/(4) xx (4)/(3) = (5)/(3)`