Long distance short - wave radio frequency broadcasting uses:

Options

A. ground wave
B. ionospheric waves
C. direct wave
D. sky wave

Answer

To solve the question regarding the use of long-distance short-wave radio frequency broadcasting, we can break it down into a series of steps:

### Step-by-Step Solution:

1. **Understanding Short-Wave Radio Frequencies**:
- Short-wave radio frequencies typically range from 3 MHz to 30 MHz. These frequencies are capable of traveling long distances due to their ability to reflect off the ionosphere.

2. **Role of the Ionosphere**:
- The ionosphere is a layer of the Earth's atmosphere that is ionized by solar radiation. It plays a crucial role in radio communication by reflecting certain radio waves back to the Earth, allowing them to travel beyond the horizon.

3. **Types of Waves**:
- There are different types of waves used in radio broadcasting:
- **Ground Waves**: These travel along the surface of the Earth and are more effective at lower frequencies.
- **Direct Waves**: These travel in a straight line from the transmitter to the receiver and are limited to line-of-sight communication.
- **Sky Waves (Ionospheric Waves)**: These waves are reflected off the ionosphere and can cover long distances, making them suitable for short-wave broadcasting.

4. **Frequency Considerations**:
- The ionosphere has a critical frequency (fc) that typically lies between 5 to 100 MHz. Frequencies above this range will not be reflected and will escape into space, which makes it important to use frequencies within this range for effective long-distance communication.

5. **Conclusion**:
- For long-distance short-wave radio frequency broadcasting, the most effective method is to use **ionospheric waves**. Therefore, the correct answer to the question is that long-distance short-wave radio frequency broadcasting uses **ionospheric waves**.

### Final Answer:
- **Ionospheric Waves** are used for long-distance short-wave radio frequency broadcasting.