The first excitation potential of a hypothetical hydrogen- like atom is `15 V`. Find the third excitation potential of the atom.

Explanation

To solve the problem of finding the third excitation potential of a hypothetical hydrogen-like atom given that the first excitation potential is 15 V, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Excitation Potential**:
- The excitation potential is the energy required to move an electron from a lower energy level to a higher energy level in an atom. For a hydrogen-like atom, the energy levels are quantized and can be calculated using the formula:
\[
E_n = -\frac{E_0}{n^2}
...