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Part 7: Light and Radiation

Photometric and radiometric quantities

66 entries· Edition 2019FR→ About this part

7-1speed of light in a medium

c

m \cdot s^{- 1}

·metre per second

phase speed of an electromagnetic wave at a given point in a medium

7-1.2

refractive index

n

1

·one

quotient of speed of light in vacuum (iso80000-1) and speed of light in a medium (t7-1.1)

7-2radiant energy <electromagnetism>

7-2.1

radiant energy

Q_{e}

W

U

(Q)

J

k g \cdot m^{2} \cdot s^{- 2}

·joule, kilogram square metre per second squared

energy (iso80000-5) emitted, transferred or received in form of electromagnetic waves

7-2.2

spectral radiant energy

Q_{e, λ}

W_{λ}

U_{λ}

(Q_{λ})

\frac{J}{n} m

k g \cdot m \cdot s^{- 2}

·joule per nanometre, kilogram metre per second squared

spectral density of radiant energy, expressed by where is radiant energy (t7-2.1) in terms of wavelength (iso80000-3)

7-3radiant energy density

7-3.1

radiant energy density

w

(ρ_{e})

\frac{J}{m^{3}}

k g \cdot m^{- 1} \cdot s^{- 2}

·joule per cubic metre, kilogram per metre second squared

volumetric density of radiant energy, expressed by where is radiant energy (t7-2.1) in an elementary three-dimensional domain and is the…

7-3.2

spectral radiant energy density in terms of wavelength

w_{λ}

\frac{J}{m^{3} \cdot n m}

k g \cdot m^{- 2} \cdot s^{- 2}

·joule per cubic metre nanometre, kilogram per square metre second squared

change of radiant energy density with wavelength, expressed by where is radiant energy density (t7-3.1) as a function of wavelength…

7-3.3

spectral radiant energy density in terms of wavenumber

w_{\tilde{ν}}

ρ_{\tilde{ν}}

\frac{J}{m^{2}}

k g \cdot s^{- 2}

·joule per square metre, kilogram per second squared

change of radiant energy density with wavenumber, expressed by where is radiant energy density (t7-3.1) as a function of wavenumber…

7-4radiant flux, radiant power

7-4.1

radiant flux, radiant power

Φ_{e}

P_{e}

(Φ, P)

W

k g \cdot m^{2} \cdot s^{- 3}

·watt, kilogram square metre per second cubed

change in radiant energy with time, expressed by where is the radiant energy (t7-2.1) emitted, transferred or received and is time…

7-4.2

spectral radiant flux, spectral radiant power

Φ_{e, λ}

P_{e, λ}

(Φ_{λ}, P_{λ})

\frac{W}{n} m

k g \cdot m \cdot s^{- 3}

·watt per nanometre, kilogram metre per second cubed

spectral density of radiant flux, expressed by where is radiant flux (t7-4.1) in terms of wavelength (iso80000-3)

7-5radiant intensity

7-5.1

radiant intensity

I_{e}

(I)

\frac{W}{s} r

k g \cdot m^{2} \cdot s^{- 3} \cdot s r^{- 1}

·watt per steradian, kilogram square metre per second cubed steradian

density of radiant flux with respect to solid angle in a specified direction, expressed by where is the radiant flux (t7-4.1) emitted in a…

7-5.2

spectral radiant intensity

I_{e, λ}

(I_{λ})

\frac{W}{s r \cdot n m}

k g \cdot m \cdot s^{- 3} \cdot s r^{- 1}

·watt per steradian nanometre, kilogram metre per second cubed steradian

spectral density of radiant intensity, expressed by where is radiant intensity (t7-5.1) in terms of wavelength (iso80000-3)

7-6radiance

7-6.1

radiance

L_{e}

(L)

\frac{W}{s r \cdot m^{2}}

k g \cdot s^{- 3} \cdot s r^{- 1}

·watt per steradian square metre, kilogram per second cubed steradian

density of radiant intensity with respect to projected area in a specified direction at a specified point on a real or imaginary surface,…

7-6.2

spectral radiance

L_{e, λ}

(L_{λ})

\frac{W}{s r \cdot m^{2} \cdot n m}

k g \cdot m^{- 1} \cdot s^{- 3} \cdot s r^{- 1}

·watt per steradian square metre nanometre, kilogram per metre second cubed steradian

density of radiance with respect to wavelength, expressed by where is radiance (t7-6.1) in terms of wavelength (iso80000-3)

7-7irradiance

7-7.1

irradiance

E_{e}

(E)

\frac{W}{m^{2}}

k g \cdot s^{- 3}

·watt per square metre, kilogram per second cubed

density of incident radiant flux with respect to area at a point on a real or imaginary surface, expressed by where is radiant flux…

7-7.2

spectral irradiance

E_{e, λ}

(E_{λ})

\frac{W}{m^{2} \cdot n m}

k g \cdot m^{- 1} \cdot s^{- 3}

·watt per square metre nanometre, kilogram per metre second cubed

density of irradiance with respect to wavelength, expressed by where is irradiance (t7-7.1) in terms of wavelength (iso80000-3)

7-8radiant exitance, DEPRECATED: radiant emittance

7-8.1

radiant exitance, DEPRECATED: radiant emittance

M_{e}

(M)

\frac{W}{m^{2}}

k g \cdot s^{- 3}

·watt per square metre, kilogram per second cubed

density of exiting radiant flux with respect to area at a point on a real or imaginary surface, expressed by where is radiant flux (t7-4.1)…

7-8.2

spectral radiant exitance

M_{e, λ}

(M_{λ})

\frac{W}{m^{2} \cdot n m}

k g \cdot m^{- 1} \cdot s^{- 3}

·watt per square metre nanometre, kilogram per metre second cubed

density of radiant exitance with respect to wavelength, expressed by where is radiant exitance (t7-8.1) in terms of wavelength (iso80000-3)

7-9radiant exposure

7-9.1

radiant exposure

H_{e}

(H)

\frac{J}{m^{2}}

k g \cdot s^{- 2}

·joule per square metre, kilogram per second squared

density of incident radiant energy with respect to area at a point on a real or imaginary surface, expressed by where is radiant energy…

7-9.2

spectral radiant exposure

H_{e, λ}

(H_{λ})

\frac{J}{m^{2} \cdot n m}

k g \cdot m^{- 1} \cdot s^{- 2}

·joule per square metre nanometre, kilogram per metre second squared

density of radiant exposure with respect to wavelength, expressed by where is radiant exposure (t7-9.1) in terms of wavelength (iso80000-3)

7-10luminous efficiency <specified photometric condition>

7-10.1

luminous efficiency

V

1

·one

quotient of radiant flux (t7-4.1) weighted by the spectral luminous efficiency (t7-10.2) and the corresponding radiant flux for a specified…

7-10.2

spectral luminous efficiency

V (λ)

1

·one

quotient of the radiant flux (t7-4.1) at wavelength and that at wavelength , such that both produce equally intense luminous sensations for…

7-11luminous efficacy of radiation <specified photometric condition>

7-11.1

luminous efficacy of radiation

K

l \frac{m}{W}

c d \cdot s r \cdot k g^{- 1} \cdot m^{- 2} \cdot s^{3}

·lumen per watt, candela steradian second cubed per kilogram square metre

quotient of luminous flux (t7-13) and the corresponding radiant flux (t7-4.1) for a specified photometric condition

7-11.2

spectral luminous efficacy

K (λ)

l \frac{m}{W}

c d \cdot s r \cdot k g^{- 1} \cdot m^{- 2} \cdot s^{3}

·lumen per watt, candela steradian second cubed per kilogram square metre

product of spectral luminous efficiency (t7-10.2) and maximum luminous efficacy (t7-11.3) for a specified photometric condition

7-11.3

maximum luminous efficacy

K_{m}

l \frac{m}{W}

c d \cdot s r \cdot k g^{- 1} \cdot m^{- 2} \cdot s^{3}

·lumen per watt, candela steradian second cubed per kilogram square metre

maximum value of spectral luminous efficacy for a specified photometric condition

7-11.4

luminous efficacy of a source

η_{v}

(η)

l \frac{m}{W}

c d \cdot s r \cdot k g^{- 1} \cdot m^{- 2} \cdot s^{3}

·lumen per watt, candela steradian second cubed per kilogram square metre

quotient of the luminous flux emitted and the power consumed by the source, expressed by where is luminous flux (t7-13) and is the power…

7-12luminous energy, DEPRECATED: quantity of light

7-12

luminous energy, DEPRECATED: quantity of light

Q_{v}

(Q)

l m \cdot s

c d \cdot s r \cdot s

·lumen second, candela steradian second

energy of electromagnetic waves weighted by the spectral luminous efficiency (t7-10.2) multiplied by maximum luminous efficacy (t7-11.3) of…

7-13luminous flux

7-13

luminous flux

Φ_{v}

(Φ)

l m

c d \cdot s r

·lumen, candela steradian

change in luminous energy with time, expressed by where is the luminous energy (t7-12) emitted, transferred or received and is time…

7-14luminous intensity

7-14

luminous intensity

I_{v}

(I)

c d

·candela

density of luminous flux with respect to solid angle in a specified direction, expressed by where is the luminous flux (t7-13) emitted in a…

7-15luminance

7-15

luminance

L_{v}

(L)

c d \cdot m^{- 2}

·candela per square metre

density of luminous intensity with respect to projected area in a specified direction at a specified point on a real or imaginary surface,…

7-16illuminance

7-16

illuminance

E_{v}

(E)

l x

c d \cdot s r \cdot m^{- 2}

·lux, candela steradian per square metre

density of incident luminous flux with respect to area at a point on a real or imaginary surface, expressed by where is luminous flux…

7-17luminous exitance

7-17

luminous exitance

M_{v}

(M)

l \frac{m}{m^{2}}

c d \cdot s r \cdot m^{- 2}

·lumen per square metre, candela steradian per square metre

density of exiting luminous flux with respect to area at a point on a real or imaginary surface, expressed by where is luminous flux…

7-18luminous exposure, DEPRECATED: quantity of illumination, DEPRECATED: light exposure

7-18

luminous exposure, DEPRECATED: quantity of illumination, DEPRECATED: light exposure

H_{v}

(H)

l x \cdot s

c d \cdot s r \cdot m^{- 2} \cdot s

·lux second, candela steradian second per square metre

density of incident luminous energy with respect to area at a point on a real or imaginary surface, expressed by where is luminous energy…

7-19photon number, number of photons

7-19.1

photon number, number of photons

N_{p}

1

·one

quotient of radiant energy and photon energy, expressed by where is radiant energy (t7-2.1), is the Planck constant (iso80000-1), and is…

7-19.2

photon energy

Q_{p}

(Q)

J

k g \cdot m^{2} \cdot s^{- 2}

·joule, kilogram square metre per second squared

product of the Planck constant and frequency, expressed by where is the Planck constant (iso80000-1) and is the frequency (iso80000-3) of…

7-20photon flux

7-20

photon flux

Φ_{p}

(Φ)

s^{- 1}

·per second

rate of photon number per time interval, expressed by where is photon number (e.g. given by t7-19.1), transmitted or received, and is time…

7-21photon intensity

7-21

photon intensity

I_{p}

(I)

s^{- 1} \cdot s r^{- 1}

·per second steradian

density of photon flux with respect to solid angle in a specified direction, expressed by where is the photon flux (t7-20) emitted in the…

7-22photon radiance

7-22

photon radiance

L_{p}

(L)

m^{- 2} \cdot s^{- 1} \cdot s r^{- 1}

·per square metre second steradian

density of photon intensity with respect to projected area in a specified direction at a specified point on a real or imaginary surface,…

7-23photon irradiance

7-23

photon irradiance

E_{p}

(E)

m^{- 2} \cdot s^{- 1}

·per square metre second

density of incident photon flux with respect to area at a point on a real or imaginary surface, expressed by where is photon flux (t7-20)…

7-24photon exitance

7-24

photon exitance

M_{p}

(M)

m^{- 2} \cdot s^{- 1}

·per square metre second

density of exiting photon flux with respect to area at a point on a real or imaginary surface, expressed by where is photon flux (t7-20)…

7-25photon exposure

7-25

photon exposure

H_{p}

(H)

m^{- 2}

·per square metre

density of incident photon number with respect to area at a point on a real or imaginary surface, expressed by where is photon number…

7-26tristimulus values for the CIE 1931 standard colorimetric observer

7-26.1

tristimulus values for the CIE 1931 standard colorimetric observer

X, Y, Z

see Remark

·see Remark

amounts of the three reference colour stimuli in the CIE 1931 standard colorimetric system, required to match the colour of the stimulus…

7-26.2

tristimulus values for the CIE 1964 standard colorimetric observer

X_{10}, Y_{10}, Z_{10}

see Remark

·see Remark

amounts of the three reference colour stimuli in the CIE 1964 standard colorimetric system, required to match the colour of the stimulus…

7-27CIE colour-matching functions for the CIE 1931 standard colorimetric observer

7-27.1

CIE colour-matching functions for the CIE 1931 standard colorimetric observer

\bar{x} (λ), \bar{y} (λ), \bar{z} (λ)

1

·one

functions , , in the CIE 1931 standard colorimetric system

7-27.2

CIE colour-matching functions for the CIE 1964 standard colorimetric observer

{\bar{x}}_{10} (λ), {\bar{y}}_{10} (λ), {\bar{z}}_{10} (λ)

1

·one

functions , , in the CIE 1964 standard colorimetric system

7-28chromaticity coordinates in the CIE 1931 standard colorimetric system

7-28.1

chromaticity coordinates in the CIE 1931 standard colorimetric system

x, y, z

1

·one

coordinates expressing the quotients of each of a set of three tristimulus values for the CIE 1931 standard colorimetric observer (t7-26.1)…

7-28.2

chromaticity coordinates in the CIE 1964 standard colorimetric system

x_{10}, y_{10}, z_{10}

1

·one

coordinates expressing the quotients of each of a set of three tristimulus values for the CIE 1964 standard colorimetric observer (t7-26.2)…

7-29colour temperature

7-29.1

colour temperature

T_{c}

K

·kelvin

temperature of a Planckian radiator whose radiation has the same chromaticity as that of a given stimulus

7-29.2

correlated colour temperature

T_{cp}

K

·kelvin

temperature of a Planckian radiator having the chromaticity nearest the chromaticity associated with the given spectral distribution on a…

7-30emissivity

7-30.1

emissivity

ε

ε_{T}

1

·one

quotient of the radiant exitance of a radiator and the radiant exitance of a Planckian radiator at the same temperature, expressed by where…

7-30.2

emissivity at a specified wavelength

ε (λ)

1

·one

quotient of the radiant exitance of a radiator at a specified wavelength and the radiant exitance of a Planckian radiator at the same…

7-31absorptance

7-31.1

absorptance

α

a

1

·one

quotient of absorbed radiant flux and incident radiant flux, expressed by where is absorbed radiant flux (t7-4.1) and is incident radiant…

7-31.2

luminous absorptance

α_{v}

1

·one

quotient of absorbed luminous flux and incident luminous flux, expressed by where is absorbed luminous flux (t7-13) and is incident…

7-31.3

reflectance

ρ

1

·one

quotient of reflected radiant flux and incident radiant flux, expressed by where is reflected radiant flux (t7-4.1) and is incident radiant…

7-31.4

luminous reflectance

ρ_{v}

1

·one

quotient of reflected luminous flux and incident luminous flux, is expressed by where is reflected luminous flux (t7-13) and is incident…

7-31.5

transmittance

τ

T

1

·one

quotient of transmitted radiant flux and incident radiant flux, expressed by where is transmitted radiant flux (t7-4.1) and is incident…

7-31.6

luminous transmittance

τ_{v}

1

·one

quotient of transmitted luminous flux and incident luminous flux, expressed by where is transmitted luminous flux (t7-13) and is luminous…

7-32transmittance optical density, optical density, transmittance density, decadic absorbance

7-32.1

transmittance optical density, optical density, transmittance density, decadic absorbance

D

A_{10}

D_{τ}

1

·one

logarithm to base 10 of the reciprocal of the transmittance, (t7-31.5)

7-32.2

Napierian absorbance

A_{n}

B

1

·one

natural (Napierian) logarithm of the reciprocal of the transmittance, (t7-31.5)

7-33radiance factor

7-33.1

radiance factor

β_{e}

(β)

1

·one

quotient of the radiance of a surface element in a specified direction and the radiance of the perfect reflecting diffuser or perfect…

7-33.2

luminance factor

β_{v}

(β)

1

·one

quotient of the luminance of a surface element in a specified direction and the luminance of the perfect reflecting diffuser or perfect…

7-34reflectance factor

7-34

reflectance factor

R

1

·one

quotient of the flux reflected in the directions delimited by a given cone with apex at a surface element and the flux reflected in the…

7-35linear attenuation coefficient, linear extinction coefficient <radiometry>

7-35.1

linear attenuation coefficient, linear extinction coefficient

μ

μ_{l}

m^{- 1}

·per metre

relative decrease in radiant flux caused by absorption and scattering

7-35.2

linear absorption coefficient

α_{l}

a_{l}

α

m^{- 1}

·per metre

relative decrease in radiant flux (t7-4.1) caused by absorption

7-36mass attenuation coefficient <radiometry>

7-36.1

mass attenuation coefficient

μ_{m}

k g^{- 1} \cdot m^{2}

·square metre per kilogram

quotient of the linear attenuation coefficient (t7-35.1), , and the mass density (iso80000-4), , of the medium

7-36.2

mass absorption coefficient

α_{m}

quotient of the linear absorption coefficient (t7-35.2), , and the mass density (iso80000-4), , of the medium

7-37molar absorption coefficient <radiometry>

7-37

molar absorption coefficient

χ

m^{2} \cdot m o l^{- 1}

·square metre per mole

product of linear absorption coefficient and molar volume, expressed by where is linear absorption coefficient (t7-35.2) and is molar…

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