Stefan-Boltzmann's law/emission spectrum

The Stefan-Boltzmann law states that every body with a temperature above absolute zero emits heat radiation.
This happens in connection with its temperature.

If a body emits radiation according to the Stefan-Boltzmann law, then the emitted spectrum is characteristic of the temperature.

The electromagnetic radiation itself can be divided into different ranges. The distinguishing feature is the wavelength. For example, a part of the radiation emitted by the sun is the light that we see.

On the left in the image is a division of the radiation of different wavelengths and frequencies. Typical representatives of radiation types are placed as images.

Electromagnetic radiation transports energy. The energy of a single "beam" depends on the wavelength (or the frequency). The shorter the wavelength (higher frequency) the higher this transported energy.

If we plot the intensity (radiation output per unit area) of an ideal heat emitter against the wavelengths, we get the specified distributions for different temperatures.

The emitted power rises with increasing temperature. Similarly, shorter wavelength and thus higher-energy radiation is emitted with increasing temperature.

As a comparison the lines in the image can be studied.
The sun radiates with a temperature of 5800K. The maximum intensity of the solar radiation is in the visible light. Besides the visible light, shorter and longer wavelength components are also contained that are not visible to the naked eye.
Steel glows above a temperature of around 800K. The line at 1000K clearly goes into the visible spectrum. You would perceive the steel as glowing bright red.

Due to the very rapid increase of the intensity, the axis follows a logarithmic representation. This has the advantage of showing values that are orders of magnitude apart. The numerical values of the scale do not increase linearly but are multiplies, see details.

The radiant power rises to the fourth power of the temperature. Doubling the temperature means a 16-fold increase in energy output by radiation. The basis in this case is the absolute temperature in kelvin. In the chart the emitted power is equal to the region below the curve.

The size of the emitting surface area is also important. The radiant power is proportional to the surface area.

The previous contents on heat radiation say a lot about the characteristics of thermal radiators. Based on the definition it is evident that there is other radiation that is not emitted by thermal radiators.

Heat radiation has a continuous, contiguous spectrum.

Similarly there are radiation sources that emit radiation but not by the mechanism of the thermal radiator. The emitted wavelength range is not related to the temperature of the radiation source. The image shows the spectrum of a red LED and a laser, which does not work in the visible spectrum.