An electron makes a transition from orbit `n = 4` to the orbit `n = 2` of a hydrogen atom. The wave number of the emitted radiations `(R =` Rydberg's constant) will be

Options

A. `(16)/(3R)`
B. `(2R)/(16)`
C. `(3R)/(16)`
D. `(4R)/(16)`

Answer

C

Explanation

Wave number is reciprocal of wavelength,
`:. " " (1)/(lambda)=R[(1)/n_(1)^(2)-(1)/(n_(2)^(2))]`
`" " v=(1)/(lambda)=R[(1)/(2^(2))-(1)/(4^(2))]`
`" " =R[(1)/(4)-(1)/(16)]=(3R)/(16)`