Critical frequency that gets reflected back from ionosphere is

Options

A. same for all layers of the ionosphere
B. different for different layers of the ionosphere
C. not dependent on layers of the ionosphere
D. None of these

Explanation

To determine the critical frequency that gets reflected back from the ionosphere, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Critical Frequency (Fc)**:
The critical frequency (Fc) is the maximum frequency at which a radio wave can be transmitted vertically and still be reflected back to Earth by the ionosphere.

2. **Formula for Critical Frequency**:
The formula for critical frequency is given by:
\[ Fc = 9 \sqrt{N_m} \]
where \(N_m\) is the electron density of the ionospheric layer.

3. **Electron Density (Nm)**:
The electron density \(N_m\) varies with different layers of the ionosphere. Each layer has its own characteristic electron density, which affects the critical frequency.

4. **Proportionality**:
From the formula, we can see that the critical frequency \(Fc\) is directly proportional to the square root of the electron density \(N_m\). This means that as the electron density increases, the critical frequency also increases.

5. **Different Layers of the Ionosphere**:
Since \(N_m\) varies for different layers of the ionosphere (such as the D, E, and F layers), the critical frequency will also differ for each layer.

6. **Conclusion**:
Therefore, the critical frequency that gets reflected back from the ionosphere is not the same for all layers; it varies depending on the electron density of each specific layer.

### Final Answer:
The critical frequency that gets reflected back from the ionosphere is different for different layers due to varying electron densities.

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