Q 12.13 Obtain an expression for the frequency of radiation emitted when a hydrogen atom de-excites from level n to level (n–1). For large n, show that this frequency equals the classical frequency of revolution of the electron in the orbit.
Using Bohr's model we have.
Since n is very large 2n-1 can be taken as 2n and n-1 as n
The frequency of the emission caused by de-excitation from n to n-1 would be
The classical frequency of revolution of the electron in the nth orbit is given by
The above is the same as the frequency of the emission during de-excitation from n to n-1.