Thermal radiations

Options

A. require no medium for their propagation.
B. heat the intervening medium through which they pass.
C. don't obey inverse square law.
D. travel with speed less than speed of light.

Explanation

### Step-by-Step Solution

**Step 1: Understanding Thermal Radiation**
- Thermal radiation refers to the electromagnetic waves emitted by all objects based on their temperature. This radiation primarily occurs in the infrared spectrum but can also include visible light and other wavelengths.

**Step 2: Propagation of Thermal Radiation**
- One of the key characteristics of thermal radiation is that it does not require a medium for propagation. This means it can travel through a vacuum, unlike sound waves, which need a medium (like air or water) to propagate.

**Step 3: Nature of Thermal Radiation**
- Thermal radiation is a form of electromagnetic radiation. Electromagnetic waves, including thermal radiation, travel at the speed of light in a vacuum. Therefore, they do not travel slower than the speed of light.

**Step 4: Examples of Thermal Radiation**
- A common example of thermal radiation is the heat we feel from the sun. Even though there is a vacuum (space) between the sun and the Earth, we can still feel the warmth because thermal radiation travels through that vacuum.

**Step 5: Conclusion**
- Based on the understanding of thermal radiation, we conclude that the correct answer to the question "What can thermal radiations do?" is that they require no medium for their propagation.