By what fraction does the mass of an H atom decreases when it makes an n=3 to n=1 transition ?

Explanation

To find the fraction by which the mass of a hydrogen atom decreases when it transitions from n=3 to n=1, we can follow these steps:

### Step 1: Determine the Energy Levels
The energy levels for a hydrogen atom are given by the formula:
\[ E_n = -\frac{13.6 \, \text{eV}}{n^2} \]
For n=1:
\[ E_1 = -\frac{13.6 \, \text{eV}}{1^2} = -13.6 \, \text{eV} \]
For n=3:
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