What is the wavelength of light emitted when the electron of a hydrogen atom undergoes a transition from an energy level with `n= 4` to an energy level with `n = 2` ? What is the colour corresponding to this wavelength?

Explanation

According to Rydberg equation,
`1/lambda = R (1/(n_1^2) - 1/(n_2^2))`
Here, `n_1 = 2, n_2 = 4 and R = 109677 cm^(-1)`
`1/lambda = 109677 (1/(2^2) - 1/(4^2)) cm^(-1)`
`=109677 (1/4 - 1/16) cm^(-1)`
`=109677 xx 12/64 cm^(-1)`
or ` lambda = (64)/(109677 xx 12) cm = 4.86 xx 10^(-5) cm`
or `lambda = 486 xx 10^(-9) m = 486 nm`
This line corresponding to bluish green colour.