Radiant Quantities and Units¶
SI Unit(s) |
Symbol |
|
---|---|---|
Flux |
W, i.e. J/s |
Φ |
Intensity |
W/sr |
I |
Exitance |
W/m2 |
M |
Irradiance |
W/m2 |
E |
Radiance |
W/sr/m2 |
L |
A prefix of “spectral” modifies the unit such that it is per wavelength or wavenumber.
Exitance and irradiance have the same units, but one refers to radiation exiting a surface and the other to radiation incident upon a surface.
A common unit for spectral radiance is the μFlick. 1 μFlick = 1 μW/sr/cm2/μm = 10-4 W/sr/m2/m.