Question

question 3. when analyzing how thermal energy moves through radiation, which of the following is not correct? a. radiation requires a medium (like air or water) to transfer heat. b. objects emit thermal radiation based on their temperature. c. all surfaces can absorb and emit thermal radiation, but some are better than others. d. thermal radiation travels in all directions from its source.

Explanation:

• Option A: Radiation does not require a medium (like air or water) to transfer heat. It can travel through a vacuum. For example, heat from the sun reaches the Earth through radiation even though there is a vacuum (space) between them.
• Option B: According to the Stefan - Boltzmann law, the power radiated by an object is proportional to \(T^{4}\) (\(P=\sigma AT^{4}\), where \(\sigma\) is the Stefan - Boltzmann constant, \(A\) is the surface area, and \(T\) is the absolute temperature). So, objects emit thermal radiation based on their temperature.
• Option C: Black bodies are perfect absorbers and emitters of thermal radiation. But in reality, different surfaces have different emissivity and absorptivity values. For example, a black - painted surface is a better absorber and emitter than a white - painted surface.
• Option D: Thermal radiation, like light (which is also an electromagnetic wave), travels in all directions from its source. This is why we can feel heat from a fire no matter what direction we are in (to some extent) around the fire.

Answer:

A. Radiation requires a medium (like air or water) to transfer heat.