Which of the following frequencies will be suitable for beyond the horizon communication using sky waves?

Options

A. 10KHz
B. 10MHz
C. 1GHz
D. 1000GHz

Explanation

To determine which frequency is suitable for beyond the horizon communication using sky waves, we need to analyze the characteristics of sky wave propagation and the behavior of different frequency ranges.

### 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 allows communication over distances beyond the horizon.

**Hint**: Remember that sky waves are used for long-distance communication where direct line-of-sight is not possible.

2. **Frequency Range Consideration**:
- Different frequencies behave differently when interacting with the ionosphere. Low frequencies (like 10 kHz) require large antennas and are not effective for long-distance communication.

**Hint**: Think about how antenna size relates to frequency; lower frequencies need larger antennas.

3. **High Frequencies**:
- Frequencies in the gigahertz range (1 GHz to 1000 GHz) tend to penetrate the ionosphere rather than being reflected. This means they cannot be used for sky wave propagation effectively.

**Hint**: High frequencies do not reflect off the ionosphere; they pass through it.

4. **Identifying Suitable Frequencies**:
- Frequencies in the range of megahertz (like 10 MHz) are effective for sky wave propagation. These frequencies can be reflected by the ionosphere, allowing signals to travel beyond the horizon.

**Hint**: Focus on the megahertz range for effective sky wave communication.

5. **Conclusion**:
- Based on the analysis, the frequency that is suitable for beyond the horizon communication using sky waves is **10 MHz**. This frequency allows for effective reflection from the ionosphere, enabling long-distance communication.

**Final Answer**: The suitable frequency for beyond the horizon communication using sky waves is **10 MHz**.