Number of spectral lines orbitals in Bohr spectrum of hydrogen atom when an electron is excited from ground level is 5th orbit is

Options

A. 10
B. 5
C. 8
D. 15

Explanation

To determine the number of spectral lines in the Bohr spectrum of a hydrogen atom when an electron is excited from the ground level to the 5th orbit, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Initial and Final Energy Levels:**
- The electron is excited from the ground state (n1 = 1) to the 5th orbit (n2 = 5).

2. **Use the Formula for Spectral Lines:**
- The formula to calculate the number of spectral lines (N) when an electron transitions from a higher energy level (n2) to a lower energy level (n1) is:
\[ N = n_2 - n_1 + 1 \]
- Additionally, we can use another formula that accounts for all possible transitions:
\[ N = \frac{n_2(n_2 - 1)}{2} \]
- This formula counts the number of ways the electron can drop from higher levels to lower levels.

3. **Substitute the Values:**
- For our case:
- n1 = 1 (ground state)
- n2 = 5 (excited state)
- Using the first formula:
\[ N = 5 - 1 + 1 = 5 \]
- Using the second formula:
\[ N = \frac{5(5 - 1)}{2} = \frac{5 \times 4}{2} = \frac{20}{2} = 10 \]

4. **Conclusion:**
- The total number of spectral lines when the electron transitions from the 5th orbit to the ground state is **10**.

### Final Answer:
The number of spectral lines in the Bohr spectrum of a hydrogen atom when an electron is excited from the ground level to the 5th orbit is **10**.