|
Radiant intensity is used to characterize the emission of radiation by an antenna.[1] Given an antenna's power density S_r (watts per square meter) when measured at some distance r from the antenna, radiation intensity is calculated by multiplying by the square of the distance: U = S_r \cdot r^2 The radiation intensity is expressed in watts per unit solid angle (watts per steradian). Unlike power density, radiation intensity does not depend on distance: because radiation intensity is defined as the power through a solid angle, the decreasing power density over distance due to the inverse-square law is offset by the increase in area with distance. Radiation intensity can as well characterize X-ray tube with filtration. X-ray tube output is defined for this purpose. SI radiometry units v t e Quantity Unit Dimension Notes Name Symbol[nb 1] Name Symbol Symbol Radiant energy Qe[nb 2] joule J M⋅L2⋅T−2 energy Radiant flux Φe[nb 2] watt W or J/s M⋅L2⋅T−3 radiant energy per unit time, also called radiant power. Spectral power Φeλ[nb 2][nb 3] watt per metre W⋅m−1 M⋅L⋅T−3 radiant power per wavelength. Radiant intensity Ie watt per steradian W⋅sr−1 M⋅L2⋅T−3 power per unit solid angle. Spectral intensity Ieλ[nb 3] watt per steradian per metre W⋅sr−1⋅m−1 M⋅L⋅T−3 radiant intensity per wavelength. Radiance Le watt per steradian per square metre W⋅sr−1⋅m−2 M⋅T−3 power per unit solid angle per unit projected source area. confusingly called "intensity" in some other fields of study. Spectral radiance Leλ[nb 3] or Leν[nb 4] watt per steradian per metre3 or watt per steradian per square metre per hertz W⋅sr−1⋅m−3 or W⋅sr−1⋅m−2⋅Hz−1 M⋅L−1⋅T−3 or M⋅T−2 commonly measured in W⋅sr−1⋅m−2⋅nm−1 with surface area and either wavelength or frequency. Irradiance Ee[nb 2] watt per square metre W⋅m−2 M⋅T−3 power incident on a surface, also called radiant flux density. sometimes confusingly called "intensity" as well. Spectral irradiance Eeλ[nb 3] or Eeν[nb 4] watt per metre3 or watt per square metre per hertz W⋅m−3 or W⋅m−2⋅Hz−1 M⋅L−1⋅T−3 or M⋅T−2 commonly measured in W⋅m−2⋅nm−1 or 10−22 W⋅m−2⋅Hz−1, known as solar flux unit.[nb 5] Radiant exitance / Radiant emittance Me[nb 2] watt per square metre W⋅m−2 M⋅T−3 power emitted from a surface. Spectral radiant exitance / Spectral radiant emittance Meλ[nb 3] or Meν[nb 4] watt per metre3 or watt per square metre per hertz W⋅m−3 or W⋅m−2⋅Hz−1 M⋅L−1⋅T−3 or M⋅T−2 power emitted from a surface per unit wavelength or frequency. Radiosity Je watt per square metre W⋅m−2 M⋅T−3 emitted plus reflected power leaving a surface. Spectral radiosity Jeλ[nb 3] watt per metre3 W⋅m−3 M⋅L−1⋅T−3 emitted plus reflected power leaving a surface per unit wavelength Radiant exposure He joule per square metre J⋅m−2 M⋅T−2 also referred to as fluence Radiant energy density ωe joule per metre3 J⋅m−3 M⋅L−1⋅T−2 In radiometry, radiant intensity is a measure of the intensity of electromagnetic radiation. It is defined as power per unit solid angle. The SI unit of radiant intensity is watts per steradian (W·sr−1). Radiant intensity is distinct from irradiance and radiant exitance, which are often called intensity in branches of physics other than radiometry. In RF engineering, radiant intensity is sometimes called radiation intensity. |
About us|Jobs|Help|Disclaimer|Advertising services|Contact us|Sign in|Website map|Search|
GMT+8, 2015-9-11 20:51 , Processed in 0.128943 second(s), 16 queries .
