irradiance

照射量

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/08/19 08:20:01」(JST)

wiki en

In radiometry, irradiance is the radiant flux received by a surface per unit area, and spectral irradiance is the irradiance of a surface per unit frequency or wavelength, depending on whether the spectrum is taken as a function of frequency or of wavelength. The SI unit of irradiance is the watt per square metre (W/m²), while that of spectral irradiance is the watt per square metre per hertz (W·m⁻²·Hz⁻¹) or the watt per square metre per metre (W·m⁻³)—commonly the watt per square metre per nanometre (W·m⁻²·nm⁻¹). The CGS unit erg per square centimeter per second (erg·cm⁻²·s⁻¹) is often used in astronomy. Irradiance is often called "intensity" in branches of physics other than radiometry, but in radiometry this usage leads to confusion with radiant intensity.

Mathematical definitions

Irradiance

Irradiance of a surface, denoted E_e ("e" for "energetic", to avoid confusion with photometric quantities), is defined as^[1]

where

∂ is the partial derivative symbol;
Φ_e is the radiant flux received;
A is the area.

If we want to talk about the radiant flux emitted by a surface, we speak of radiant exitance.

Spectral irradiance

Spectral irradiance in frequency of a surface, denoted E_e,ν, is defined as^[1]

where ν is the frequency.

Spectral irradiance in wavelength of a surface, denoted E_e,λ, is defined as^[1]

where λ is the wavelength.

Property

Irradiance of a surface is also, according to the definition of radiant flux, equal to the time-average of the component of the Poynting vector perpendicular to the surface:

where

< • > is the time-average;
S is the Poynting vector;
n is a unit vector normal to that surface;
α is the angle between n and S.

For a propagating sinusoidal linearly polarized electromagnetic plane wave, the Poynting vector always points to the direction of propagation while oscillating in magnitude. The irradiance of a surface is then given by^[2]

where

E_m is the amplitude of the wave's electric field;
n is the refractive index of the medium of propagation;
c is the speed of light in vacuum;
μ₀ is the vacuum permeability;
ε₀ is the vacuum permittivity.

This formula assumes that the magnetic susceptibility is negligible, i.e. that μ_r ≈ 1 where μ_r is the magnetic permeability of the propagation medium. This assumption is typically valid in transparent media in the optical frequency range.

Solar energy

The global irradiance on a horizontal surface on Earth consists of the direct irradiance E_e,dir and diffuse irradiance E_e,diff. On a tilted plane, there is another irradiance component, E_e,refl, which is the component that is reflected from the ground. The average ground reflection is about 20% of the global irradiance. Hence, the irradiance E_e on a tilted plane consists of three components:^[3]

The integral of solar irradiance over a time period is called "solar exposure" or "insolation".^[3]^[4]

SI radiometry units

SI radiometry units

Quantity		Unit		Dimension	Notes
Name	Symbol^{[nb 1]}	Name	Symbol	Symbol	Notes
Radiant energy	Q_e^{[nb 2]}	joule	J	M⋅L²⋅T⁻²	Energy of electromagnetic radiation.
Radiant energy density	w_e	joule per cubic metre	J/m³	M⋅L⁻¹⋅T⁻²	Radiant energy per unit volume.
Radiant flux	Φ_e^{[nb 2]}	watt	W or J/s	M⋅L²⋅T⁻³	Radiant energy emitted, reflected, transmitted or received, per unit time. This is sometimes also called "radiant power".
Spectral flux	Φ_e,ν^{[nb 3]} or Φ_e,λ^{[nb 4]}	watt per hertz or watt per metre	W/Hz or W/m	M⋅L²⋅T⁻² or M⋅L⋅T⁻³	Radiant flux per unit frequency or wavelength. The latter is commonly measured in W⋅sr⁻¹⋅m⁻²⋅nm⁻¹.
Radiant intensity	I_e,Ω^{[nb 5]}	watt per steradian	W/sr	M⋅L²⋅T⁻³	Radiant flux emitted, reflected, transmitted or received, per unit solid angle. This is a directional quantity.
Spectral intensity	I_e,Ω,ν^{[nb 3]} or I_e,Ω,λ^{[nb 4]}	watt per steradian per hertz or watt per steradian per metre	W⋅sr⁻¹⋅Hz⁻¹ or W⋅sr⁻¹⋅m⁻¹	M⋅L²⋅T⁻² or M⋅L⋅T⁻³	Radiant intensity per unit frequency or wavelength. The latter is commonly measured in W⋅sr⁻¹⋅m⁻²⋅nm⁻¹. This is a directional quantity.
Radiance	L_e,Ω^{[nb 5]}	watt per steradian per square metre	W⋅sr⁻¹⋅m⁻²	M⋅T⁻³	Radiant flux emitted, reflected, transmitted or received by a surface, per unit solid angle per unit projected area. This is a directional quantity. This is sometimes also confusingly called "intensity".
Spectral radiance	L_e,Ω,ν^{[nb 3]} or L_e,Ω,λ^{[nb 4]}	watt per steradian per square metre per hertz or watt per steradian per square metre, per metre	W⋅sr⁻¹⋅m⁻²⋅Hz⁻¹ or W⋅sr⁻¹⋅m⁻³	M⋅T⁻² or M⋅L⁻¹⋅T⁻³	Radiance of a surface per unit frequency or wavelength. The latter is commonly measured in W⋅sr⁻¹⋅m⁻²⋅nm⁻¹. This is a directional quantity. This is sometimes also confusingly called "spectral intensity".
Irradiance	E_e^{[nb 2]}	watt per square metre	W/m²	M⋅T⁻³	Radiant flux received by a surface per unit area. This is sometimes also confusingly called "intensity".
Spectral irradiance	E_e,ν^{[nb 3]} or E_e,λ^{[nb 4]}	watt per square metre per hertz or watt per square metre, per metre	W⋅m⁻²⋅Hz⁻¹ or W/m³	M⋅T⁻² or M⋅L⁻¹⋅T⁻³	Irradiance of a surface per unit frequency or wavelength. The former is commonly measured in 10⁻²² W⋅m⁻²⋅Hz⁻¹, known as solar flux unit, and the latter in W⋅m⁻²⋅nm⁻¹.^{[nb 6]} This is sometimes also confusingly called "spectral intensity".
Radiosity	J_e^{[nb 2]}	watt per square metre	W/m²	M⋅T⁻³	Radiant flux leaving (emitted, reflected and transmitted by) a surface per unit area. This is sometimes also confusingly called "intensity".
Spectral radiosity	J_e,ν^{[nb 3]} or J_e,λ^{[nb 4]}	watt per square metre per hertz or watt per square metre, per metre	W⋅m⁻²⋅Hz⁻¹ or W/m³	M⋅T⁻² or M⋅L⁻¹⋅T⁻³	Radiosity of a surface per unit frequency or wavelength. The latter is commonly measured in W⋅m⁻²⋅nm⁻¹. This is sometimes also confusingly called "spectral intensity".
Radiant exitance	M_e^{[nb 2]}	watt per square metre	W/m²	M⋅T⁻³	Radiant flux emitted by a surface per unit area. This is the emitted component of radiosity. "Radiant emittance" is an old term for this quantity. This is sometimes also confusingly called "intensity".
Spectral exitance	M_e,ν^{[nb 3]} or M_e,λ^{[nb 4]}	watt per square metre per hertz or watt per square metre, per metre	W⋅m⁻²⋅Hz⁻¹ or W/m³	M⋅T⁻² or M⋅L⁻¹⋅T⁻³	Radiant exitance of a surface per unit frequency or wavelength. The latter is commonly measured in W⋅m⁻²⋅nm⁻¹. "Spectral emittance" is an old term for this quantity. This is sometimes also confusingly called "spectral intensity".
Radiant exposure	H_e	joule per square metre	J/m²	M⋅T⁻²	Radiant energy received by a surface per unit area, or equivalently irradiance of a surface integrated over time of irradiation. This is sometimes also called "radiant fluence".
Spectral exposure	H_e,ν^{[nb 3]} or H_e,λ^{[nb 4]}	joule per square metre per hertz or joule per square metre, per metre	J⋅m⁻²⋅Hz⁻¹ or J/m³	M⋅T⁻¹ or M⋅L⁻¹⋅T⁻²	Radiant exposure of a surface per unit frequency or wavelength. The latter is commonly measured in J⋅m⁻²⋅nm⁻¹. This is sometimes also called "spectral fluence".
Hemispherical emissivity	ε			1	Radiant exitance of a surface, divided by that of a black body at the same temperature as that surface.
Spectral hemispherical emissivity	ε_ν or ε_λ			1	Spectral exitance of a surface, divided by that of a black body at the same temperature as that surface.
Directional emissivity	ε_Ω			1	Radiance emitted by a surface, divided by that emitted by a black body at the same temperature as that surface.
Spectral directional emissivity	ε_Ω,ν or ε_Ω,λ			1	Spectral radiance emitted by a surface, divided by that of a black body at the same temperature as that surface.
Hemispherical absorptance	A			1	Radiant flux absorbed by a surface, divided by that received by that surface. This should not be confused with "absorbance".
Spectral hemispherical absorptance	A_ν or A_λ			1	Spectral flux absorbed by a surface, divided by that received by that surface. This should not be confused with "spectral absorbance".
Directional absorptance	A_Ω			1	Radiance absorbed by a surface, divided by the radiance incident onto that surface. This should not be confused with "absorbance".
Spectral directional absorptance	A_Ω,ν or A_Ω,λ			1	Spectral radiance absorbed by a surface, divided by the spectral radiance incident onto that surface. This should not be confused with "spectral absorbance".
Hemispherical reflectance	R			1	Radiant flux reflected by a surface, divided by that received by that surface.
Spectral hemispherical reflectance	R_ν or R_λ			1	Spectral flux reflected by a surface, divided by that received by that surface.
Directional reflectance	R_Ω			1	Radiance reflected by a surface, divided by that received by that surface.
Spectral directional reflectance	R_Ω,ν or R_Ω,λ			1	Spectral radiance reflected by a surface, divided by that received by that surface.
Hemispherical transmittance	T			1	Radiant flux transmitted by a surface, divided by that received by that surface.
Spectral hemispherical transmittance	T_ν or T_λ			1	Spectral flux transmitted by a surface, divided by that received by that surface.
Directional transmittance	T_Ω			1	Radiance transmitted by a surface, divided by that received by that surface.
Spectral directional transmittance	T_Ω,ν or T_Ω,λ			1	Spectral radiance transmitted by a surface, divided by that received by that surface.
Hemispherical attenuation coefficient	μ	reciprocal metre	m⁻¹	L⁻¹	Radiant flux absorbed and scattered by a volume per unit length, divided by that received by that volume.
Spectral hemispherical attenuation coefficient	μ_ν or μ_λ	reciprocal metre	m⁻¹	L⁻¹	Spectral radiant flux absorbed and scattered by a volume per unit length, divided by that received by that volume.
Directional attenuation coefficient	μ_Ω	reciprocal metre	m⁻¹	L⁻¹	Radiance absorbed and scattered by a volume per unit length, divided by that received by that volume.
Spectral directional attenuation coefficient	μ_Ω,ν or μ_Ω,λ	reciprocal metre	m⁻¹	L⁻¹	Spectral radiance absorbed and scattered by a volume per unit length, divided by that received by that volume.
See also: SI · Radiometry · Photometry

^ Standards organizations recommend that radiometric quantities should be denoted with suffix "e" (for "energetic") to avoid confusion with photometric or photon quantities.
^ ^a ^b ^c ^d ^e Alternative symbols sometimes seen: W or E for radiant energy, P or F for radiant flux, I for irradiance, W for radiant exitance.
^ ^a ^b ^c ^d ^e ^f ^g Spectral quantities given per unit frequency are denoted with suffix "ν" (Greek)—not to be confused with suffix "v" (for "visual") indicating a photometric quantity.
^ ^a ^b ^c ^d ^e ^f ^g Spectral quantities given per unit wavelength are denoted with suffix "λ" (Greek).
^ ^a ^b Directional quantities are denoted with suffix "Ω" (Greek).
^ NOAA / Space Weather Prediction Center includes a definition of the solar flux unit (SFU).

References

^ ^a ^b ^c "Thermal insulation — Heat transfer by radiation — Physical quantities and definitions". ISO 9288:1989. ISO catalogue. 1989. Retrieved 2015-03-15.
^ Griffiths, David J. (1999). Introduction to electrodynamics (3. ed., reprint. with corr. ed.). Upper Saddle River, NJ [u.a.]: Prentice-Hall. ISBN 0-13-805326-X.
^ ^a ^b Quaschning, Volker (2003). "Technology fundamentals—The sun as an energy resource". Renewable Energy World 6 (5): 90–93.
^ Liu, B. Y. H.; Jordan, R. C. (1960). "The interrelationship and characteristic distribution of direct, diffuse and total solar radiation". Solar Energy 4 (3): 1. doi:10.1016/0038-092X(60)90062-1. edit

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

1. 皮膚病変に対するレーザーおよびインテンスパルスライトの原理 principles of laser and intense pulsed light for cutaneous lesions
2. 正期産児および後期早産児における非抱合型高ビリルビン血症の治療 treatment of unconjugated hyperbilirubinemia in term and late preterm infants
3. UVA1療法 uva1 phototherapy
4. 早産児（妊娠35週未満）における高ビリルビン血症 hyperbilirubinemia in the premature infant less than 35 weeks gestation
5. 医療用レーザーの基本原則 basic principles of medical lasers

English Journal

Scale-Up of flat plate photobioreactors considering diffuse and direct light characteristics.

Quinn JC, Turner CW, Bradley TH.SourceDepartment of Mechanical Engineering, A103R Engineering, 1374 Campus Delivery, Colorado State University, Fort Collins, Colorado 80523-1374; telephone: 970-581-7992; fax: 970-491-3827.
Biotechnology and bioengineering.Biotechnol Bioeng.2012 Feb;109(2):363-70. doi: 10.1002/bit.23324. Epub 2011 Sep 19.
This study investigates the scaling of photobioreactor productivity based on the growth of Nannochloropsis salina incorporating the effects of direct and diffuse light. The scaling and optimization of photobioreactor geometry was analyzed by determining the growth response of a small-scale system de
PMID 21915850

Thylakoid protein phosphorylation in dynamic regulation of photosystem II in higher plants.

Tikkanen M, Aro EM.AbstractIn higher plants, the photosystem (PS) II core and its several light harvesting antenna (LHCII) proteins undergo reversible phosphorylation cycles according to the light intensity. High light intensity induces strong phosphorylation of the PSII core proteins and suppresses the phosphorylation level of the LHCII proteins. Decrease in light intensity, in turn, suppresses the phosphorylation of PSII core, but strongly induces the phosphorylation of LHCII. Reversible and differential phosphorylation of the PSII-LHCII proteins is dependent on the interplay between the STN7 and STN8 kinases, and the respective phosphatases. The STN7 kinase phosphorylates the LHCII proteins and to a lesser extent also the PSII core proteins D1, D2 and CP43. The STN8 kinase, on the contrary, is rather specific for the PSII core proteins. Mechanistically, the PSII-LHCII protein phosphorylation is required for optimal mobility of the PSII-LHCII protein complexes along the thylakoid membrane. Physiologically, the phosphorylation of LHCII is a prerequisite for sufficient excitation of PSI, enabling the excitation and redox balance between PSII and PSI under low irradiance, when excitation energy transfer from the LHCII antenna to the two photosystems is efficient and thermal dissipation of excitation energy (NPQ) is minimised. The importance of PSII core protein phosphorylation is manifested under highlight when the photodamage of PSII is rapid and phosphorylation is required to facilitate the migration of damaged PSII from grana stacks to stroma lamellae for repair. The importance of thylakoid protein phosphorylation is highlighted under fluctuating intensity of light where the STN7 kinase dependent balancing of electron transfer is a prerequisite for optimal growth and development of the plant. This article is part of a Special Issue entitled: Photosystem II.
Biochimica et biophysica acta.Biochim Biophys Acta.2012 Jan;1817(1):232-8. Epub 2011 May 14.
In higher plants, the photosystem (PS) II core and its several light harvesting antenna (LHCII) proteins undergo reversible phosphorylation cycles according to the light intensity. High light intensity induces strong phosphorylation of the PSII core proteins and suppresses the phosphorylation level
PMID 21605541

Japanese Journal

The Bunsen-Roscoe reciprocity law in ultraviolet-B-induced mortality of the two-spotted spider mite Tetranychus urticae.

Murata Yasumasa,Osakabe Masahiro
Journal of insect physiology 59(3), 241-247, 2013-03-00
… To determine whether the Bunsen-Roscoe reciprocity law (i.e., the extent of photochemical effects is determined by cumulative irradiance) is applicable to ultraviolet-B (UVB) damage in the twospotted spider mite Tetranychus urticae, egg hatchability and survival of individuals were assessed after irradiation with a UVB lamp using various combinations of intensity and time length. …
NAID 120005242564

Solar radiation transfer in the surface snow layer in Dronning Maud Land, Antarctica

Jarvinen Onni,Lepparanta Matti
Polar science 7(1), 1-17, 2013-03-00
… Using the spectral extinction coefficients of the 0-10-cm and 10-20-cm layers, the depth, where broadband (400-700-nm band) irradiance was 1% of the downwelling irradiance at the surface, was 50 cm. …
NAID 110009575376

防蛾用黄色LED光がキクの開花反応に及ぼす影響

石倉聡,梶原真二,福島啓吾,後藤丹十郎
岡山大学農学部学術報告 102, 35-41, 2013-02-01
… As irradiance increased, the days to flower budding increased except under blue light. … There was no difference in the crown bud number and the occurrence of abnormal flower irrespective of the light quality and irradiance. … The minimum irradiance strength enough for flower inhibition in the continuous lighting treatment was about 80 mW m−2 that was half in night break treatment. …
NAID 120005222609

Related Pictures

[note-suffix-e-5] Standards organizations recommend that radiometric quantities should be denoted with suffix "e" (for "energetic") to avoid confusion with photometric or photon quantities.

[note-alternative-symbol-radiometric-6] Alternative symbols sometimes seen: W or E for radiant energy, P or F for radiant flux, I for irradiance, W for radiant exitance.

[note-suffix-nu-7] ^ ^a ^b ^c ^d ^e ^f ^g Spectral quantities given per unit frequency are denoted with suffix "ν" (Greek)—not to be confused with suffix "v" (for "visual") indicating a photometric quantity.

[note-suffix-lambda-8] ^ ^a ^b ^c ^d ^e ^f ^g Spectral quantities given per unit wavelength are denoted with suffix "λ" (Greek).

[note-suffix-omega-9] Directional quantities are denoted with suffix "Ω" (Greek).

[note-NOAA-SFU-10] NOAA / Space Weather Prediction Center includes a definition of the solar flux unit (SFU).

[ISO_9288-1989-1] "Thermal insulation — Heat transfer by radiation — Physical quantities and definitions". ISO 9288:1989. ISO catalogue. 1989. Retrieved 2015-03-15.

[griffiths-2] Griffiths, David J. (1999). Introduction to electrodynamics (3. ed., reprint. with corr. ed.). Upper Saddle River, NJ [u.a.]: Prentice-Hall. ISBN 0-13-805326-X.

[Quaschning-3] Quaschning, Volker (2003). "Technology fundamentals—The sun as an energy resource". Renewable Energy World 6 (5): 90–93.

[4] Liu, B. Y. H.; Jordan, R. C. (1960). "The interrelationship and characteristic distribution of direct, diffuse and total solar radiation". Solar Energy 4 (3): 1. doi:10.1016/0038-092X(60)90062-1. edit

匿名

検索

案内

案内

irradiance

目次

Wikipedia preview

wiki en

Contents

Mathematical definitions

Irradiance

Spectral irradiance

Property

Solar energy

SI radiometry units

See also

References

UpToDate Contents

English Journal

Japanese Journal

Related Links

Related Pictures