In a single isolated atom an electron make transition from 5th excited state to 2nd state then maximum number of different types of photons observed is

Explanation

To solve the problem of how many different types of photons can be observed when an electron transitions from the 5th excited state to the 2nd state in a single isolated atom, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Energy Levels:**
- The energy levels of an atom are typically denoted by principal quantum numbers (n). The ground state is n=1, the first excited state is n=2, and so on.
- The 5th excited state corresponds to n=6 (since the ground state is n=1, the first excited state is n=2, and so forth).

2. **Identifying the Transition:**
- The electron transitions from the 5th excited state (n=6) to the 2nd state (n=2).

3. **Using the Formula for Maximum Spectral Lines:**
- The maximum number of different types of spectral lines (or photons) that can be observed during a transition from n2 to n1 is given by the formula:
\[ \text{Maximum Spectral Lines} = n_2 - n_1 \]
- Here, \( n_2 = 6 \) (the initial state) and \( n_1 = 2 \) (the final state).

4. **Calculating the Number of Spectral Lines:**
- Substitute the values into the formula:
\[ \text{Maximum Spectral Lines} = 6 - 2 = 4 \]

5. **Understanding the Transitions:**
- The transitions that can occur are:
- From n=6 to n=5 (1 photon)
- From n=5 to n=4 (1 photon)
- From n=4 to n=3 (1 photon)
- From n=3 to n=2 (1 photon)
- Each of these transitions emits a photon, leading to a total of 4 different types of photons.

6. **Final Answer:**
- Therefore, the maximum number of different types of photons observed when the electron transitions from the 5th excited state to the 2nd state is **4**.