31 Facts About Black-body radiation

Black-body radiation is the thermal electromagnetic radiation within, or surrounding, a body in thermodynamic equilibrium with its environment, emitted by a black body .

Thermal radiation spontaneously emitted by many ordinary objects can be approximated as black-body radiation.

Particular importance, although planets and stars are neither in thermal equilibrium with their surroundings nor perfect black bodies, black-body radiation is still a good first approximation for the energy they emit.

The sun's Black-body radiation, after being filtered by the earth's atmosphere, thus characterises "daylight", which humans have evolved to use for vision.

Black-body radiation is called thermal radiation, cavity radiation, complete radiation or temperature radiation.

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Black-body radiation has a characteristic, continuous frequency spectrum that depends only on the body's temperature, called the Planck spectrum or Planck's law.

Black-body radiation provides insight into the thermodynamic equilibrium state of cavity radiation.

The Black-body radiation represents a conversion of a body's internal energy into electromagnetic energy, and is therefore called thermal Black-body radiation.

An object that absorbs all Black-body radiation falling on it, at all wavelengths, is called a black body.

Black-body radiation has the unique absolutely stable distribution of radiative intensity that can persist in thermodynamic equilibrium in a cavity.

In equilibrium, for each frequency, the intensity of Black-body radiation which is emitted and reflected from a body relative to other frequencies is determined solely by the equilibrium temperature and does not depend upon the shape, material or structure of the body.

Black-body radiation becomes a visible glow of light if the temperature of the object is high enough.

The hole, then, is a close approximation of a theoretical black body and, if the cavity is heated, the spectrum of the hole's Black-body radiation will be continuous, and will depend only on the temperature and the fact that the walls are opaque and at least partly absorptive, but not on the particular material of which they are built nor on the material in the cavity .

Real objects never behave as full-ideal black bodies, and instead the emitted Black-body radiation at a given frequency is a fraction of what the ideal emission would be.

Hawking radiation is the hypothetical black-body radiation emitted by black holes, at a temperature that depends on the mass, charge, and spin of the hole.

Since there are an infinite number of modes, this would imply infinite heat capacity, as well as a nonphysical spectrum of emitted Black-body radiation that grows without bound with increasing frequency, a problem known as the ultraviolet catastrophe.

Wavelength at which the Black-body radiation is strongest is given by Wien's displacement law, and the overall power emitted per unit area is given by the Stefan–Boltzmann law.

Cosmic microwave background radiation observed today is the most perfect black-body radiation ever observed in nature, with a temperature of about 2.

Black-body radiation says that Newton imagined particles of light traversing space uninhibited by the caloric medium filling it, and refutes this view by saying that a black body under illumination would increase indefinitely in heat.

Black-body radiation was concerned with selective thermal radiation, which he investigated with plates of substances that radiated and absorbed selectively for different qualities of radiation rather than maximally for all qualities of radiation.

Black-body radiation did not in this paper mention that the qualities of the rays might be described by their wavelengths, nor did he use spectrally resolving apparatus such as prisms or diffraction gratings.

Black-body radiation made his measurements in a room temperature environment, and quickly so as to catch his bodies in a condition near the thermal equilibrium in which they had been prepared by heating to equilibrium with boiling water.

Black-body radiation's measurements confirmed that substances that emit and absorb selectively respect the principle of selective equality of emission and absorption at thermal equilibrium.

Black-body radiation made no mention of thermodynamics in this paper, though he did refer to conservation of vis viva.

Black-body radiation proposed that his measurements implied that radiation was both absorbed and emitted by particles of matter throughout depths of the media in which it propagated.

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Black-body radiation concluded that his experiments showed that in a cavity in thermal equilibrium, the heat radiated from any part of the interior bounding surface, no matter of what material it might be composed, was the same as would have been emitted from a surface of the same shape and position that would have been composed of lamp-black.

Black-body radiation did not state explicitly that the lamp-black-coated bodies that he used as reference must have had a unique common spectral emittance function that depended on temperature in a unique way.

Black-body radiation's principle has endured: it was that for heat rays of the same wavelength, in equilibrium at a given temperature, the wavelength-specific ratio of emitting power to absorptivity has one and the same common value for all bodies that emit and absorb at that wavelength.

Black-body radiation's proof noted that the dimensionless wavelength-specific absorptivity of a perfectly black body is by definition exactly 1.

Black-body radiation argued that the flows of heat radiation must be the same in each case.

Black-body radiation supposed that like other functions that do not depend on the properties of individual bodies, it would be a simple function.