| Term | Symbol | Quantity | Unit | 
|---|---|---|---|
| radiant energy[?] | Q | energy | joule (J) | 
| radiant power[?] Synonym optical power | φ | power | watt (W) | 
| irradiance[?] | E | power incident per unit area (irrespective of angle) | W·m-2 | 
| spectral irradiance[?] | Eλ | irradiance[?] per unit wavelength interval at a given wavelength | W·m-2·nm-1 | 
| radiant emittance[?] Synonym radiant exitance | W | power emitted (into a full sphere) per unit area | W·m-2 | 
| radiant intensity[?] | I | power per unit solid angle | W·sr-1 | 
| radiance[?] | L | power per unit angle per unit projected area | W·sr-1·m-2 | 
| spectral radiance[?] | Lλ | radiance[?] per unit wavelength interval at a given wavelength | W·sr-1·m-2·nm-1 | 
Source: from Federal Standard 1037C
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