The audio signal

Options

A. can be sent directly over the air for large distance
B. cannot be sent directly over the air for large distance
C. possess very high frequency.
D. none of these

Answer

To solve the question regarding the speed at which heat radiation propagates, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Nature of Heat Radiation**:
- Heat radiation is a form of energy transfer that occurs through electromagnetic waves.

2. **Understand Electromagnetic Waves**:
- Electromagnetic waves include a range of phenomena such as radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X-rays, and gamma rays.

3. **Determine the Speed of Electromagnetic Waves**:
- All electromagnetic waves travel at the same speed in a vacuum, which is the speed of light (approximately \(3 \times 10^8\) meters per second).

4. **Analyze the Given Options**:
- The options provided are:
- (a) Alpha ray
- (b) Beta ray
- (c) Light waves
- (d) Sound wave
- Among these, alpha and beta rays are types of particles and do not represent electromagnetic radiation. Sound waves are mechanical waves and do not travel at the speed of light.

5. **Select the Correct Option**:
- Since heat radiation is an electromagnetic wave, it propagates at the same speed as light waves. Therefore, the correct answer is option (c) Light waves.

### Final Answer:
The heat radiation propagates with the speed of light waves, which corresponds to option (c).

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