If the de Broglie wave length of the fourth Bohr's orbit of hydrogen atom is 4 Å, the circumference of the orbit is:

Options

A. `4 Å`
B. 4nm
C. `16 Å`
D. 16 nm

Explanation

To solve the problem, we need to find the circumference of the fourth Bohr orbit of a hydrogen atom given that the de Broglie wavelength (λ) of that orbit is 4 Ångströms (Å).

### Step-by-Step Solution:

1. **Identify the given values:**
- The de Broglie wavelength (λ) = 4 Å
- The principal quantum number (n) for the fourth Bohr orbit = 4

2. **Use the relationship between circumference and wavelength:**
The circumference (C) of the orbit can be expressed as:
\[ C = n \cdot \lambda \]
where:
- \( n \) is the principal quantum number,
- \( \lambda \) is the de Broglie wavelength.

3. **Substitute the known values into the equation:**
\[ C = 4 \cdot 4 \, \text{Å} \]
\[ C = 16 \, \text{Å} \]

4. **Conclusion:**
The circumference of the fourth Bohr orbit of the hydrogen atom is 16 Å.

### Final Answer:
The circumference of the orbit is **16 Å**.