Blackbody radiation origins

The origins of quantum theory blackbody radiation and the photoelectric effect... 

The Origins of Quantum Theory Blackbody Radiation and the Photoelectric Effect... 

Three discoveries mark the transition from classical to modem physics quantum theory, radioactivity, and relativity (Fig. 4.1). Quantum theory had its origin in the study of blackbody radiation and the photoelectric effect. 

By definition, photometers do not respond to radiation in the infrared or the ultraviolet (Fig. 4-4a). They are light meters in the sense that they mimic human vision that is, they respond to photons in the visible region, similar to the light meter on a camera. A candle is a unit of luminous intensity, originally based on a standard candle or lamp. The current international unit is called a candela (sometimes still referred to as a candle ), which was previously defined as the total light intensity of 1.67 mm2 of a blackbody radiator (one that radiates maximally) at the melting temperature of pure platinum (2042 K). In 1979 the candela was redefined as the luminous intensity of a monochromatic source with a frequency of 5.40 x 1014 cycles s-1 (A, of 555 nm) emitting 0.01840 Js-1 or 0.01840 W (1.464 mW steradian-1, where W is the abbreviation for watt and steradian... 

The origin of blackbody radiation was a major challenge to 19th Century physics. Lord Rayleigh proposed that the electromagnetic field could be represented by... 

A preliminary version of the SOFM method was also applied to a commercial oil-fired burner with a nominal capacity of 60 kW. The flames in this case were yellow and highly radiating, with characteristics (physical and visual) very different from those of the blue flames described. In particular, the nature and origin of emission spectra are expected to be deeply different dominated by blackbody radiation from soot particles, with a much smaller contribution due to chemiluminescence of excited radicals. An exercise similar to that reported in Section 15.4.4 was performed to estimate NO concentration from flame images. The NO emissions varied in the range of 53 to 94 ppm for the flames analyzed the estimation error was within 5 ppm in practically all cases, very similar in relative terms to the results shown in Figure 15.7. 

When the squares of the halfwidth Au of the signal curves are plot-tedversus the Rydberg atom flux, a straight line is obtained as expected. This line intersects the (Au) axis at a finite value, from which the number of blackbody photons originally in the cavity can be evaluated. The result (3 + 1) is in reasonable agreement with the value given above. It follows that as the atomic flux decreases the thermal radiation becomes the dominant part of the field [15]. 

Radiation that is emitted by the surface originates from the thermal energy of matter bounded by the surface. The rate at which energy is released per unit area Wjvr ) is determined by the surface emissive power E. For a blackbody the emissive power (representing a theoretical maximum rate) is prescribed by the Stefan-Boltzmann law ... 

A particularly striking example of this is the visible light emission from some porous silicon and silicon nanoparticle structures originally ascribed to photoluminescence but later revealed to be blackbody thermal radiation by careful experimentation (Costa et al. 1998 Roura and Costa 2002). Some very spectrally broad cathodoluminescence spectra published are also likely to be primarily thermal radiation, as discussed in the handbook chapter Cathodoluminescence of Porous Silicon. ... 

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