Feketetestsugárzás

Feketetestsugárzás, also known as black-body radiation, is the electromagnetic radiation that is emitted from an opaque surface. This radiation is a consequence of the object's temperature. All objects with a temperature above absolute zero emit black-body radiation. The term "black body" refers to an idealized object that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. Because it absorbs all radiation, it is also a perfect emitter of radiation.

The spectrum of black-body radiation is continuous and depends only on the temperature of the body. At low temperatures, the radiation is primarily in the infrared part of the spectrum, and is therefore invisible to the human eye. As the temperature increases, the peak of the emitted radiation shifts towards shorter wavelengths, and the object begins to glow, first red, then orange, yellow, and eventually white or blue.

The spectral distribution of black-body radiation was famously described by Max Planck, whose work on this subject in 1900 laid the foundation for quantum mechanics. Planck's law quantifies the intensity of radiation emitted at each wavelength as a function of temperature. Two other important laws related to black-body radiation are Wien's displacement law, which states that the wavelength at which the emitted radiation is most intense is inversely proportional to the temperature, and the Stefan-Boltzmann law, which states that the total energy radiated per unit surface area of a black body is directly proportional to the fourth power of its absolute temperature. Black-body radiation is a fundamental concept in thermodynamics and astrophysics.