Black body

Black body is a theoretical or model body which absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. A black body in thermodynamic equilibrium emits electromagnetic radiation called black-body radiation. The radiation is emitted according to Planck's law, meaning that it has a specific spectrum and intensity that depends only on the temperature of the body.

Overview

The concept of the black body is an idealization, as perfect black bodies do not exist in nature. However, some graphite and black holes can come close to the characteristics of a black body. The black body is used in a variety of scientific models and calculations, including quantum mechanics, particle physics, and astronomy.

Black-body radiation

Black-body radiation is the type of electromagnetic radiation within or surrounding a body in thermodynamic equilibrium with its environment, emitted by a black body. It has a specific spectrum of wavelengths, inversely related to intensity that depend only on the body's temperature, which is assumed for the sake of calculations and theory to be uniform and constant.

Planck's law

Planck's law describes the spectral density of electromagnetic radiation emitted by a black body in thermal equilibrium at a given temperature T. The law is named after Max Planck, who proposed it in 1900. It was the first quantum theory in history and provided the foundation of quantum mechanics.

Applications

Black bodies have many practical applications. In physics, they are used for calibration of light-sensitive devices. In astronomy, the concept of the black body is used to estimate the temperature of celestial bodies. In climate science, black-body radiation is used to model the energy balance of the Earth's systems.

See also

• Stefan–Boltzmann law
• Wien's displacement law
• Rayleigh–Jeans law