Irradiation (physical quantity)

Physical size
Surname	Irradiation
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:

• Irradiation instruments, lamps, UV lamps, material processing
• Skin diseases (see also 308 nm excimer laser )
• Lacquer and glue hardening, as well as the irradiation of radiation-sensitive "photo" lacquers (especially in microlithography when UV radiation is used)
• Drinking water treatment using UV light
• Energy measurement on pulsed lasers in which the physical effect is primarily determined by pulse energy and pulse duration.

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))

References and comments

1. ↑ Although in English the “radiant exposure” is sometimes inconsistently referred to as “radiometric fluence” (fluence)