Body measurements Info

The solar constant is the amount of solar radiation received outside the earths atmosphere on a surface normal to the incident radiation per unit time and per unit area at earths mean distance from the sun. The experiment used a black body approach to experimentally measure plancks reduced constant by using the planck radiation law which relates the intensity and wavelength of light to the temperature of the emitting black body. The measurement was accomplished by using a simplified detection system involving a. From the time that kirchhoff enunciated the principle that the intensity of radiation from a black body is dependent only upon the wavelength of the radiation and the temperature of the radiating body a relationship worth while investigation the theoretical treatment of the radiation problem has provided a rich fertile source of fresh discoveries. Indeed a black body can also emit radiation. The black body radiation they produce is well behaved and in accordance to the parameters that the developer sets.

A nice example of black body radiation is that left over from the big bang. It has been found that the intensity pattern of this background radiation in the universe follows the black body curve very precisely for a temperature of about three degrees above absolute zero. Black body radiation is the thermal electromagnetic radiation within or surrounding a body in thermodynamic equilibrium with its environment emitted by a black body an idealized opaque non reflective body. On the contrary a white body is one with a rough surface that reflects all incident. A black body or blackbody is an idealized physical body that absorbs all incident electromagnetic radiation regardless of frequency or angle of incidencethe name black body is given because it absorbs radiation in all frequencies not because it only absorbs. The solar radiation fits closely with the black body emission in the visible and infrared region at this temperature but deviates in the uv region.

When developing a new method of thermal imaging this allows for the accuracy of the technology to be tested to values as accurate as the black body radiation source will allow. In the high wavelength limit the rayleigh jeans expression for black body intensity i p for a radiation temperature t at wavelength λ is given by 2 i p 2 c k b t λ 4. It has a specific spectrum of wavelengths inversely related to intensity that depend only on the bodys temperature which is assumed for the sake of calculations and theory to be. Optical pyrometers use the rayleigh jeans expression 12 to measure temperatures of hot solid objects radiating as black bodies.