The wavelength of a monochromatic light in vacuum is 4000 Å. It's wave number in glass of refractive index 1.6 is

Options

A. `1 xx 10^(6) m^(-1)`
B. `2 xx 10^(6) m^(-1)`
C. `3 xx 10^(6) m^(-1)`
D. `4 xx 10^(6) m^(-1)`

Answer

D

Explanation

`mu_(g) = (lambda_(a))/(lambda_(g))`
`:. bar(lambda)_(g) = (1)/(lambda_(g)) = (mu_(g))/(lambda_(a)) = (1.6)/(4 xx 10^(-7)) = 4 xx 10^(6) m^(-1)`