The mode of propagation used by short wave broadcast services is

Options

A. space wave
B. sky wave
C. ground wave
D. both a and c

Answer

To solve the question regarding the mode of propagation used by short wave broadcast services, we can break it down into the following steps:

### Step 1: Understand the Frequency Range
Short wave broadcast services operate within a specific frequency range. This range is typically from a few megahertz up to about 30 to 40 megahertz.

**Hint:** Remember that frequency ranges are crucial in determining the mode of propagation.

### Step 2: Identify the 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 significant role in radio wave propagation. For short wave frequencies, the ionosphere acts as a reflector.

**Hint:** Consider how different atmospheric layers interact with radio waves at various frequencies.

### Step 3: Determine the Mode of Propagation
For short wave broadcast services, the mode of propagation that is primarily used is known as sky wave propagation. This occurs when the radio waves are reflected off the ionosphere, allowing them to travel beyond the horizon.

**Hint:** Think about how radio waves can travel long distances by bouncing off the ionosphere.

### Step 4: Conclusion
Based on the above understanding, we conclude that the mode of propagation used by short wave broadcast services is sky wave propagation.

**Final Answer:** The mode of propagation used by short wave broadcast services is **sky wave propagation**.

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