Question

In which of the following does transfer of heat through electromagnetic waves occur?
${\text{A}}{\text{.}}$ Conduction
${\text{B}}{\text{.}}$ Convection
${\text{C}}{\text{.}}$ Radiation
${\text{D}}{\text{.}}$ All of these

Answer 1

Hint: Here, we will proceed by defining all the different heat transfer processes mentioned in the options of the given problem (i.e., conduction, convection and radiation). Then, we will write down their causes of heat transfer.

Complete step-by-step answer:

Conduction transfers heat through direct molecular collision. An area with greater kinetic energy will transfer thermal energy to a lower kinetic energy area. Particulates of higher speed can collide with particles of slower speed. As a result, the slower-speed particles will result in the increase in kinetic energy. Conduction is the most common method of heat transfer, and it takes place by physical contact. Examples may be pressing your hand against a glass, or putting metal in an open flame.

If a gas, such as air or liquid, is heated and then flows away from the source, the thermal energy is brought along. This form of transfer of heat is called convection. The fluid over a hot surface is expanding, becoming less dense and growing.

At the molecular level the molecules expand when thermal energy is added. When the temperature of the given fluid mass increases, it must increase the volume of the fluid by the same amount. The fluid effect causes displacement. It forces out denser, cooler air as the subsequent hot air rises.

Thermal radiation is produced from electromagnetic wave emissions. Such waves take away the energy from the body that emits it. Radiation takes place in a vacuum, or through some transparent medium (solid or fluid). Thermal radiation is the direct product of the spontaneous motions in the matter between atoms and molecules. Movement of the charged protons and electrons results in electromagnetic radiation emissions.

Therefore, the heat transfer through electromagnetic waves occurs in the process named radiation.

Hence, option C is correct.

Note: The heat conduction process depends on the following factors which includes temperature gradient, material cross-section, travel path length and physical properties of the material. Based on their temperature all materials radiate thermal energy. The hotter an object becomes, the more it radiates.