Question

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

Answer 1

We have,

Energy level $n=4$ and $n=2$

According to the Balmer series

Wave no $=RH[\frac{1}{n_1^2}-\frac{1}{n_2^2}]$

Here $n_1=2,n_2=4$

Putting the value then we get,

Wave number $=109678(\frac{1}{2^2}-\frac{1}{4^2})$

$=\frac{109678\times 3}{16}$

Also,

$\lambda =\frac{1}{waveno}$

Therefore,

$\lambda =\frac{16}{109678\times 3}=486nm$