| Q |
Radiant energy |
Total energy radiated in all directions
|
 |
J |
| W |
Radiant Density |
Total energy radiated by a unit area in all directions
|
 |
J/m3
|
| F
|
Radiant flux (power)
|
Total energy radiated in all directions for
a unit of time
|
Φ |
J/s, W |
| M |
Radiant exitance |
Total energy radiated in all directions by a
unit area in a unit time
|
 |
W/m2
|
| E
|
Irradiance |
Total energy radiated onto a unit area in unit
time
|
 |
W/m2
|
| I
|
Radiant Intensity |
Total energy per unit solid angle of measurement
|
 |
W/sr
|
| L
|
Radiance
|
Total energy radiated by a unit area per unit
solid angle of measurement.
|
 |
W/(m2-sr)
|
| Mλ
|
Spectral radiant exitance |
Energy radiated within a wavelength band in
all directions by a unit area in a unit time
|
 |
W/(m2- µm)
|
| Eλ
|
Spectral irradiance |
Energy radiated within a wavelength band onto
a unit area in unit time
|
 |
W/(m2- µm) |
| Lλ
|
Spectral radiance |
Energy within a wavelength band radiated by
a unit area per unit solid angle of measurement |
 |
W/(m2-sr-m)
|
| ε
|
Emissivity
|
Ratio of radiant exitance of the surface ( M )
with a perfectly emitting surface called
the blackbody (M Blackbody )
|
 |
Unitless
|
| ρ |
Reflectance
|
Ratio of the incident (Φi)
to reflected (Φr) radiant flux
|
 |
Unitless
|
| α |
Absorptance |
Ratio of the incident (Φi) to
absorbed (Φα) radiant flux
|
 |
Unitless |
| τ |
Transmittance
|
Ratio of the incident (Φi) to
absorbed (Φτ) radiant flux
|
 |
Unitless |
