Which of the transitions in hydrogen atom emits a photon of lowest frequecny `(n =` quantum number)?

Options

A. `n = 2` to `n = 1`
B. `n = 4` to `n = 3`
C. `n = 3` to `n = 1`
D. `n = 4` to `n = 2`

Answer

B

Explanation

From diagram

`E_(1) =- 13.6 - (-3.4) =- 10.2 eV`
`E_(2) =- 13.6 - (-1.51) =- 12.09 eV`
`E_(3) =- 1.51 - (-0.85) =- 0.66 eV`
`E_(4) =- 3.4 - (-1.51) =- 0.89 eV`
`E_(3)` is least i.e., frequency is lowest.