microwatt per square centimeter
Intensityexact by definition
The microwatt per square centimetre is exactly 0.01 watts per square metre. It is the unit of ultraviolet germicidal irradiance, where a UVC radiometer reads directly in μW/cm² and a dose in mJ/cm² is that irradiance times exposure time, and it is also used for radiofrequency exposure surveys. The conversion is exact, following from the exact definition of the centimetre.
Watch out: A germicidal dose is irradiance times time, so a low irradiance held for longer is equivalent to a high one held briefly, up to the point where repair mechanisms in the organism keep pace. Lamp output also falls with age and with cold air flow across the tube, so a design figure needs an end-of-life derating rather than the initial rating.
| 1 μW/cm² | 0.01 W/m² |