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As the radiation pressure scales as the fourth power of the temperature, it becomes important at these high temperatures. In the Sun, radiation pressure is still quite small when compared to the gas pressure. In the heaviest non-degenerate stars, radiation pressure is the dominant pressure component. [25]
Gas exchange is the physical process by which gases move passively by diffusion across a surface. For example, this surface might be the air/water interface of a water body, the surface of a gas bubble in a liquid, a gas-permeable membrane, or a biological membrane that forms the boundary between an organism and its extracellular environment.
Several sources [2] [12] [3] replace nσ λ with k λ r, where k λ is the absorption coefficient per unit density and r is the density of the gas. The absorption coefficient for spectral flux (a beam of radiation with a single wavelength, [W/m 2 /μm]) differs from the absorption coefficient for spectral intensity [W/sr/m 2 /μm] used in ...
The grey atmosphere (or gray) is a useful set of approximations made for radiative transfer applications in studies of stellar atmospheres (atmospheres of stars) based on the simplified notion that the absorption coefficient of matter within a star's atmosphere is constant—that is, unchanging—for all frequencies of the star's incident radiation.
Eddington assumed the pressure P in a star is a combination of an ideal gas pressure and radiation pressure, and that there is a constant ratio, β, of the gas pressure to the total pressure. Therefore, by the ideal gas law: = where k B is Boltzmann constant and μ the mass of a single atom (actually, an ion since matter is ionized; usually a ...
Pressure due to direct impact of a strong breeze (~28 mph or 45 km/h) [27] [28] [31] 120 Pa Pressure from the weight of a U.S. quarter lying flat [32] [33] 133 Pa 1 torr ≈ 1 mmHg [34] ±200 Pa ~140 dB: Threshold of pain pressure level for sound where prolonged exposure may lead to hearing loss [citation needed] ±300 Pa ±0.043 psi
Also required are the equations of state, relating the pressure, opacity and energy generation rate to other local variables appropriate for the material, such as temperature, density, chemical composition, etc. Relevant equations of state for pressure may have to include the perfect gas law, radiation pressure, pressure due to degenerate ...
Radiative transfer (also called radiation transport) is the physical phenomenon of energy transfer in the form of electromagnetic radiation. The propagation of radiation through a medium is affected by absorption , emission , and scattering processes.