chapter6
... The light from a star is usually concentrated in a rather narrow range of wavelengths. The spectrum of a star’s light is approximately a thermal spectrum called black body spectrum. A perfect black body emitter would not reflect any radiation. Thus the name ‘black body’. ...
... The light from a star is usually concentrated in a rather narrow range of wavelengths. The spectrum of a star’s light is approximately a thermal spectrum called black body spectrum. A perfect black body emitter would not reflect any radiation. Thus the name ‘black body’. ...
Blackbody Radiation, Stellar temperature and types
... astrophysical object with no reference to the observer. The observed flux density for an observer at a distance d from a star with radius r* is: ...
... astrophysical object with no reference to the observer. The observed flux density for an observer at a distance d from a star with radius r* is: ...
Chapter 4: Spectroscopy
... the molecules must be discreet • Only transitions by an amount E=hf are allowed • The implication is that light is discreet or quantised ...
... the molecules must be discreet • Only transitions by an amount E=hf are allowed • The implication is that light is discreet or quantised ...
Lecture 2
... Under certain circumstances this may not be true (e.g., electron scattering). In this case the photon energy distribution will deviate from the Planck spectrum and one has the more general Bode-Einstein distribution, with a mean occupation number: ...
... Under certain circumstances this may not be true (e.g., electron scattering). In this case the photon energy distribution will deviate from the Planck spectrum and one has the more general Bode-Einstein distribution, with a mean occupation number: ...
Missouri Club for Homework 1 The Electromagnetic Spectrum
... area is given by Steffan-Boltzmann Law: • E = σ T4 • Increase with temperature is very steep: factor of 2 for a factor of 1.2 in temperature interactive Wien’s law ...
... area is given by Steffan-Boltzmann Law: • E = σ T4 • Increase with temperature is very steep: factor of 2 for a factor of 1.2 in temperature interactive Wien’s law ...
Black body
A black body (also blackbody) is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. A white body is one with a ""rough surface [that] reflects all incident rays completely and uniformly in all directions.""A black body in thermal equilibrium (that is, at a constant temperature) emits electromagnetic radiation called black-body radiation. The radiation is emitted according to Planck's law, meaning that it has a spectrum that is determined by the temperature alone (see figure at right), not by the body's shape or composition.A black body in thermal equilibrium has two notable properties:It is an ideal emitter: at every frequency, it emits as much energy as – or more energy than – any other body at the same temperature.It is a diffuse emitter: the energy is radiated isotropically, independent of direction.An approximate realization of a black surface is a hole in the wall of a large enclosure (see below). Any light entering the hole is reflected indefinitely or absorbed inside and is unlikely to re-emerge, making the hole a nearly perfect absorber. The radiation confined in such an enclosure may or may not be in thermal equilibrium, depending upon the nature of the walls and the other contents of the enclosure.Real materials emit energy at a fraction—called the emissivity—of black-body energy levels. By definition, a black body in thermal equilibrium has an emissivity of ε = 1.0. A source with lower emissivity independent of frequency often is referred to as a gray body.Construction of black bodies with emissivity as close to one as possible remains a topic of current interest.In astronomy, the radiation from stars and planets is sometimes characterized in terms of an effective temperature, the temperature of a black body that would emit the same total flux of electromagnetic energy.