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Transfer of Heat
Radiation
All bodies with a temperature > 0 K emit energy in the form of electromagnetic waves (due to the movement of atoms in the body). These waves are absorbed by anything that comes into their path. When the energy is absorbed by another body, its temperature increases.
- Higher temperature bodies emit more radiation than lower temperature ones.
- The wavelength of the radiation is inversely related to the temperature (ie. shorter wavelength radiation results from higher temperatures).
- Electromagnetic waves can travel through a vacuum.
Both the sun and earth emit thermal radiation, although solar radiation is of a shorter wavelength (hence, greater intensity) due to its higher temperatures.
Conduction
Conduction is heat transfer between bodies in contact. While the earth's surface is heated by solar radiation, air in contact with the earth is heated by conduction.
Convection
Liquids and gases (collectively known as fluids) can transfer heat by convection. When a fluid is heated, it becomes less dense, causing it to move towards parts of the fluid of different density (and temperature). Heat then transfers between the two parts.
An example of convection is the vertical movement of hot air as it rises.
Advection
Although not completely synonymous with convection in scientific terms, in meteorology it is effectively used as such, and represents the horizontal displacement of air, while convection is vertical.