Sky wave propagation is not possible for waves of frequency`gt ` 30 MHz because

Options

A. these waves do not have much energy to reach ionosphere
B. they are not reflected by ionosphere
C. they get absorbed by troposphere
D. they get reflected by stratosphere

Answer

To solve the question regarding why sky wave propagation is not possible for waves of frequency greater than 30 MHz, we can break down the explanation into clear steps:

### Step-by-Step Solution:

1. **Understanding Sky Wave Propagation**:
- Sky wave propagation refers to the transmission of radio waves that are reflected back to Earth by the ionosphere. This typically occurs for frequencies between 3 MHz and 30 MHz.

2. **Role of the Ionosphere**:
- The ionosphere is a layer of the Earth's atmosphere that is ionized by solar and cosmic radiation. It plays a crucial role in reflecting certain radio frequencies back to Earth.

3. **Frequency Limitations**:
- Waves with frequencies below 30 MHz can be reflected by the ionosphere due to their interaction with the ionized particles present in that layer. However, as the frequency increases beyond 30 MHz, the behavior of these waves changes.

4. **Behavior of Waves Above 30 MHz**:
- For frequencies greater than 30 MHz, the energy of the waves increases. These high-frequency waves do not have the same interaction with the ionosphere as lower frequencies do. Instead of being reflected, they tend to pass through the ionosphere.

5. **Conclusion**:
- Therefore, sky wave propagation is not possible for frequencies greater than 30 MHz because these waves are not reflected by the ionosphere. They are transmitted directly through it, which prevents them from returning to Earth and thus eliminates the possibility of sky wave propagation.

### Final Answer:
Sky wave propagation is not possible for waves of frequency greater than 30 MHz because these waves are not reflected by the ionosphere.

---