Thermal radiation

Thermal radiation is a type of electromagnetic radiation that is emitted by an object due to its temperature. It is a fundamental process by which energy is transported in the universe.

Overview

Thermal radiation is generated when heat from the movement of charged particles within atoms is converted to electromagnetic radiation. The emitted wave frequency of thermal radiation is a probability distribution that is determined by the temperature of the emitting object, with the peak frequency increasing with temperature. This relationship is described by Planck's law.

Mechanism

The mechanism of thermal radiation is fundamentally quantum mechanical in nature. When a particle moves in the presence of an electromagnetic field, it can absorb or emit radiation. The energy of the emitted or absorbed radiation is quantized, meaning it can only occur in discrete amounts, which are proportional to the frequency of the radiation. This is described by the Planck-Einstein relation.

Properties

Thermal radiation has several important properties. It does not require any medium to propagate, meaning it can travel through the vacuum of space. This is how the Sun's energy reaches Earth. The intensity and frequency distribution of thermal radiation depends solely on the temperature of the emitting body. This property allows for the temperature of distant objects in space to be determined through spectral analysis.

Applications

Thermal radiation has many practical applications. It is used in thermal imaging, where cameras detect the thermal radiation emitted by objects and use this information to create an image. It is also used in thermography, where thermal radiation is used to detect heat leaks in buildings and machines, and in pyrometry, for measuring high temperatures.

See also

• Black body
• Stefan–Boltzmann law
• Wien's displacement law