Wave number is

Options

A. `lamda `
B. `1/ lamda `
C. `(c )/(lamda)`
D. ` lamda xx v `

Answer

### Step-by-Step Solution:

1. **Understanding Wave Number**:
- Wave number is defined as the number of wavelengths per unit distance. It quantifies how many wavelengths fit into a given length.

2. **Symbol and Units**:
- The symbol for wave number is represented as \( \tilde{\nu} \) (nu bar).
- The unit of wave number is typically given in reciprocal centimeters (cm\(^{-1}\)).

3. **Mathematical Representation**:
- The wave number \( \tilde{\nu} \) is mathematically expressed as:
\[ \tilde{\nu} = \frac{1}{\lambda} \]
- Here, \( \lambda \) represents the wavelength.

4. **Identifying the Correct Option**:
- Given the options, we need to identify which one correctly represents wave number:
- Option A: \( \lambda \) (Incorrect)
- Option B: \( \frac{1}{\lambda} \) (Correct)
- Option C: \( \frac{C}{\lambda} \) (Incorrect, as \( C \) is the speed of light)
- Option D: \( \lambda \cdot \nu \) (Incorrect)

5. **Conclusion**:
- The correct answer is Option B: \( \frac{1}{\lambda} \).