The number of waves, contained in unit length of the medium, is called

Options

A. wave pulse
B. wave number
C. elastic wave
D. electromagnetic wave

Answer

To solve the question, "The number of waves contained in unit length of the medium is called," we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Waves**:
- A wave is a disturbance that travels through a medium, transferring energy from one point to another.

2. **Identify Key Terms**:
- The question mentions "number of waves" and "unit length." This suggests we need to relate these terms to a specific concept in wave physics.

3. **Define Wavelength**:
- Wavelength (λ) is the distance between two consecutive crests (or troughs) of a wave.

4. **Relate Wavelength to Number of Waves**:
- If we consider a unit length (1 meter, for example), the number of waves that fit into this length can be calculated by dividing the unit length by the wavelength.

5. **Introduce Wave Number**:
- The wave number (n) is defined as the number of wavelengths per unit length. It is mathematically expressed as:
\[ n = \frac{1}{\lambda} \]
- This means that the wave number is the reciprocal of the wavelength.

6. **Select the Correct Answer**:
- Given the options:
1. Wave pulse
2. Wave number
3. Elastic wave
4. Electronic wave
- The correct answer is **Wave number** (Option 2), as it directly refers to the number of waves contained in a unit length of the medium.

### Final Answer:
The number of waves contained in unit length of the medium is called **Wave number**.

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