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Spectral irradiance is the irradiance of a surface per unit frequency or ... this equation indicates that doubling the distance reduces irradiation to one quarter; or ...
Irradiance Flux density: E e [nb 2] watt per square metre W/m 2: M⋅T −3: Radiant flux received by a surface per unit area. This is sometimes also confusingly called "intensity". Spectral irradiance Spectral flux density: E e,ν [nb 3] watt per square metre per hertz W⋅m −2 ⋅Hz −1: M⋅T −2: Irradiance of a surface per unit ...
Irradiance Flux density: E e [nb 2] watt per square metre W/m 2: M⋅T −3: Radiant flux received by a surface per unit area. This is sometimes also confusingly called "intensity". Spectral irradiance Spectral flux density: E e,ν [nb 3] watt per square metre per hertz W⋅m −2 ⋅Hz −1: M⋅T −2: Irradiance of a surface per unit ...
When an area element is radiating as a result of being illuminated by an external source, the irradiance (energy or photons /time/area) landing on that area element will be proportional to the cosine of the angle between the illuminating source and the normal. A Lambertian scatterer will then scatter this light according to the same cosine law ...
This integrated solar irradiance is called solar irradiation, solar radiation, solar exposure, solar insolation, or insolation. Irradiance may be measured in space or at the Earth's surface after atmospheric absorption and scattering. Irradiance in space is a function of distance from the Sun, the solar cycle, and cross-cycle changes. [2]
Mathematically, for the spectral power distribution of a radiant exitance or irradiance one may write: =where M(λ) is the spectral irradiance (or exitance) of the light (SI units: W/m 2 = kg·m −1 ·s −3); Φ is the radiant flux of the source (SI unit: watt, W); A is the area over which the radiant flux is integrated (SI unit: square meter, m 2); and λ is the wavelength (SI unit: meter, m).
At Earth, this energy is passing through a sphere with a radius of a 0, the distance between the Earth and the Sun, and the irradiance (received power per unit area) is given by = The Earth has a radius of R ⊕ , and therefore has a cross-section of π R ⊕ 2 {\displaystyle \pi R_{\oplus }^{2}} .
Radiant intensity is used to characterize the emission of radiation by an antenna: [2], = (), where E e is the irradiance of the antenna;; r is the distance from the antenna.; Unlike power density, radiant intensity does not depend on distance: because radiant intensity is defined as the power through a solid angle, the decreasing power density over distance due to the inverse-square law is ...