Sky wave propagation is used in

Options

A. radio communication
B. satellite communication
C. TV communication
D. both TV and satellite communication

Answer

### Step-by-Step Solution:

1. **Understanding Sky Wave Propagation**:
- Sky wave propagation refers to the transmission of radio waves from a transmitter to a receiver via reflection from the ionosphere.

2. **Diagram Representation**:
- Visualize the scenario: Draw a diagram with the Earth, a transmitter, a receiver, and the ionosphere.
- The transmitter sends radio waves that travel upward and are reflected back to Earth by the ionosphere.

3. **Frequency Range**:
- Identify the frequency range suitable for sky wave propagation.
- It is known that the frequency of waves used for this type of communication typically falls between 3 kHz to 30 MHz.

4. **Application of Sky Wave Propagation**:
- Determine the applications of sky wave propagation.
- It is primarily used in radio communication, especially for long-distance transmission.

5. **Conclusion**:
- Based on the understanding of sky wave propagation and its frequency range, we conclude that it is used in **radio communication**.

### Final Answer:
- Sky wave propagation is used in **radio communication**.

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