| Abstract from DBPedia | A radiometer or roentgenometer is a device for measuring the radiant flux (power) of electromagnetic radiation. Generally, a radiometer is an infrared radiation detector or an ultraviolet detector. Microwave radiometers operate in the microwave wavelengths. While the term radiometer can refer to any device that measures electromagnetic radiation (e.g. light), the term is often used to refer specifically to a Crookes radiometer ("light-mill"), a device invented in 1873 in which a rotor (having vanes which are dark on one side, and light on the other) in a partial vacuum spins when exposed to light. A common belief (one originally held even by Crookes) is that the momentum of the absorbed light on the black faces makes the radiometer operate. If this were true, however, the radiometer would spin away from the non-black faces, since the photons bouncing off those faces impart more momentum than the photons absorbed on the black faces. Photons do exert radiation pressure on the faces, but those forces are dwarfed by other effects.The currently accepted explanation depends on having just the right degree of vacuum, and relates to the transfer of heat rather than the direct effect of photons. A Nichols radiometer demonstrates photon pressure. It is much more sensitive than the Crookes radiometer and it operates in a complete vacuum, whereas operation of the Crookes radiometer requires an imperfect vacuum. The MEMS radiometer can operate on the principles of Nichols or Crookes and can operate over a wide spectrum of wavelength and particle energy levels.放射計(ほうしゃけい、Radiometer)とは、電磁波の放射電力を測定する機器である。ラジオメーターとも呼ばれる。 一般的に、放射計といえば、赤外線の放射を測定する機器を指すが、赤外線以外の周波数領域でも使われる。 赤外線放射計の、電磁波検出装置は、多くの場合、ボロメータ型であり、赤外線の吸収による温度の上昇を温度計で測定することで、間接的に放射電力量を知ることができる。温度の増加量は、入射する放射電波の電力量に比例する。 また、マイクロ波領域の電磁放射を計測する機器、マイクロ波放射計という。 (Source: http://dbpedia.org/resource/Radiometer) |
