Derive an expression for the frequency of radiation emitted when a hydrogen atom de-excites from level n to level (n – 1). Also show that for large values of n, this frequency equals to classical frequency of revolution of an electron.

Explanation

To derive the expression for the frequency of radiation emitted when a hydrogen atom de-excites from level \( n \) to level \( n-1 \), we will follow these steps:

### Step 1: Determine the Energy Levels of the Hydrogen Atom
The energy of an electron in a hydrogen atom at a principal quantum number \( n \) is given by the formula:

\[ E_n = -\frac{m z^2 e^4}{8 \epsilon_0^2 h^2} \cdot \frac{1}{n^2} \]
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