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 gbalmer equation
Wavelength `(bar v) = R_(H) [(1)/(n_(1)^(2)) - (1)/(n_(2)^(2))] cm^(-1)`
`n_(1) = 2,n_(2) = 4, R_(H) = 109677 cm^(-1)`
substituting all the value , we get
`bar v = 109677 [(1)/((2)^(2)) - (1)/((4)^(2))] cm^(-1) = (10977 xx 3)/(16) cm^(-1)`
`or lambda = (1)/(bar v ) = (16)/(109677 xx 3) cm = 486 nm `
The wavelength corresponds to blue colour