No. of visible lines when an electron returns from `5^(th)` orbit up to ground state in `H`spectrum :

Options

A. `5`
B. `4`
C. `3`
D. `10`

Explanation

To find the number of visible lines when an electron returns from the 5th orbit to the ground state in the hydrogen spectrum, we will follow these steps:

### Step 1: Identify the relevant series
The visible lines in the hydrogen spectrum correspond to the Balmer series. The Balmer series is defined for transitions where the final energy level (n) is 2.

### Step 2: Determine the initial and final energy levels
In this case, the electron is transitioning from the 5th orbit (n = 5) to the ground state (n = 1) and also to the second level (n = 2). The transitions we need to consider for the Balmer series are:
- From n = 5 to n = 2
- From n = 5 to n = 3
- From n = 5 to n = 4

### Step 3: Calculate the number of possible transitions
The possible transitions from n = 5 to lower energy levels (n = 4, n = 3, and n = 2) are:
1. n = 5 to n = 2
2. n = 5 to n = 3
3. n = 5 to n = 4

### Step 4: Count the visible lines
Since the only transition that results in visible light is from n = 5 to n = 2, we have:
- Transition from n = 5 to n = 2 (1 visible line)
- Transition from n = 5 to n = 3 (not visible)
- Transition from n = 5 to n = 4 (not visible)

Thus, the only visible transition that contributes to the Balmer series is from n = 5 to n = 2.

### Conclusion
The total number of visible lines when an electron returns from the 5th orbit to the ground state in the hydrogen spectrum is **3** (from n = 5 to n = 2, n = 5 to n = 3, and n = 5 to n = 4).