100% modulation in FM means

Options

A. actual frequency deviation `gt` maximum allowed frequency deviation
B. actual frequency deviation = maximum allowed frequency deviation
C. actual frequency deviation `ge` maximum allowed frequency deviation
D. actual frequency deviation `lt ` maximum allowed frequency deviation

Explanation

To understand what 100% modulation in frequency modulation (FM) means, we can break it down step by step.

### Step-by-Step Solution:

1. **Understanding Modulation**:
- Modulation is the process of varying one or more properties of a periodic waveform (the carrier signal) in accordance with a modulating signal (the information signal).

2. **Modulation Index (M)**:
- The modulation index (M) in frequency modulation is defined as the ratio of the actual frequency deviation (Δf) to the maximum allowed frequency deviation (Δf_max).
- Mathematically, it is expressed as:
\[ M = \frac{\Delta f}{\Delta f_{max}} \]

3. **Defining 100% Modulation**:
- 100% modulation means that the actual frequency deviation is equal to the maximum allowed frequency deviation.
- This can be expressed as:
\[ M = 1 \quad \text{(or 100%)} \]

4. **Conclusion**:
- Therefore, when we say there is 100% modulation in FM, it indicates that the modulation index (M) is equal to 1, meaning the actual frequency deviation is at its maximum allowed value.

### Final Answer:
100% modulation in frequency modulation means that the actual frequency deviation is equal to the maximum allowed frequency deviation, resulting in a modulation index (M) of 1.

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