Physical size
Formula symbol ${\ displaystyle H}$ , ${\ displaystyle H _ {\ mathrm {e}}}$ Size and
unit system
unit dimension
SI J · m -2 M · T −2

The irradiation or irradiation is a physical quantity , mainly in the radiometry is used. It is the time-integrated irradiance and indicates the incident radiation energy of electromagnetic radiation per area. The symbol for irradiation is , the SI unit is joules per square meter (J / m 2 ). In the case of accumulating receivers (e.g. a photo plate ), the irradiation is a measure of the area-related potential of the radiation. ${\ displaystyle H}$ Irradiation should not be confused with fluence ; the latter is a particle-related quantity (unit of measurement m −2 ).

## definition

For a given location, the irradiation can be expressed as the radiation energy Q per area or, equivalent, as the integral of the irradiance E over the given period of time . ${\ displaystyle \ Delta t}$ ${\ displaystyle H = {\ frac {\ mathrm {d} Q} {\ mathrm {d} A}} = \ int _ {\ Delta t} E (t) \ mathrm {d} t}$ The photometric equivalent of the radiation, that is, weighted with the sensitivity of the human eye, is the exposure H v .

## use

This size is also used in technical, scientific, but also medical areas:

The duration of the irradiation depends on the application and may be specified separately. The time interval to which the measurement relates can range from a few attoseconds (ultrashort pulse laser) to hours ( sunburn ) to years (fading of car paintwork). A reference variable for the time interval often emerges from the application.

## Relationship with other radiometric quantities

 radiometric quantity Symbol a) SI unit description photometric equivalent b) symbol SI unit Radiant flux radiant power, radiant flux, radiant power ${\ displaystyle \ Phi _ {\ mathrm {e}}}$ W ( watt ) Radiant energy through time Luminous flux luminous flux, luminous power ${\ displaystyle \ Phi _ {\ mathrm {v}}}$ lm ( lumens ) Radiant intensity irradiance, radiant intensity ${\ displaystyle I _ {\ mathrm {e}}}$ W / sr Radiation flux through solid angles Luminous intensity luminous intensity ${\ displaystyle I _ {\ mathrm {v}}}$ cd = lm / sr ( candela ) Irradiance irradiance ${\ displaystyle E _ {\ mathrm {e}}}$ W / m 2 Radiation flux through the receiver surface Illuminance illuminance ${\ displaystyle E _ {\ mathrm {v}}}$ lx = lm / m 2 ( lux ) Specific radiation emission current density, radiant exitance ${\ displaystyle M _ {\ mathrm {e}}}$ W / m 2 Radiation flux through the transmitter surface Specific light emission luminous exitance ${\ displaystyle M _ {\ mathrm {v}}}$ lm / m 2 Radiance radiance, radiance, radiance ${\ displaystyle L _ {\ mathrm {e}}}$ W / m 2 sr Radiant intensity through effective transmitter area Luminance luminance ${\ displaystyle L _ {\ mathrm {v}}}$ cd / m 2 Radiant energy amount of radiation, radiant energy ${\ displaystyle Q _ {\ mathrm {e}}}$ J ( joules ) by radiation transmitted energy Amount of light luminous energy, quantity of light ${\ displaystyle Q _ {\ mathrm {v}}}$ lm · s Irradiation irradiation, radiant exposure ${\ displaystyle H _ {\ mathrm {e}}}$ J / m 2 Radiant energy through the receiver surface Exposure luminous exposure ${\ displaystyle H _ {\ mathrm {v}}}$ lx s Radiation yield radiant efficiency ${\ displaystyle \ eta _ {\ mathrm {e}}}$ 1 Radiation flux through absorbed (mostly electrical) power Luminous efficiency (overall) luminous efficacy ${\ displaystyle \ eta _ {\ mathrm {v}}}$ lm / W
a)The index "e" is used to distinguish it from the photometric quantities. It can be omitted.
b)The photometric quantities are the radiometric quantities, weighted with the photometric radiation equivalent K , which indicates the sensitivity of the human eye.

## literature

• Ludwig Bergmann , Clemens Schaefer : Optics . 9th edition. Walter de Gruyter, Berlin 1993, ISBN 3-11-012973-6 (textbook on experimental physics; 3).
• Commission Électrotechnique Internationale (CEI): Vocabulaire international de l'éclairage . Publication CIE No. 17.4. Central Bureau of the CEI. 1987. (Vocabulaire électrotechnique international 50 (845))