Is there any research on how much EM radiation applied to human skin will cause significant pain (I guess an appropriate unit of measurement for the amount of radiation would be Watt/cm^2, not sure how to measure pain)? It also depends on the wavelength, I am interested in the visible part of the spectrum. Pain sensations would also depend on exactly where the radiation is being applied, I am interested in the back (but e.g. index finger is probably much more sensitive).
As @Carey says in his comment, measuring pain is very subjective to the individual, and their reporting of pain levels. It doesn't have any way of scientific measurement.
Wikipedia has a list of 'pain scales'.
ElectroMagnetic Radiation has some thresholds at which things happen, such as:
- Sufficiently strong electromagnetic radiation (EMR) can cause electric currents in conductive materials that is strong enough to create sparks (electrical arcs) when an induced voltage exceeds the breakdown voltage of the surrounding medium (e.g. air at 3.0 MV/m). These can deliver an electric shock to persons or animals.
- Radio frequency (RF) energy at power density levels of 1-10 mW/cm^2 or higher can cause measurable heating of tissues.
And WHO are investigating further: