1) The wavelength of the radiation emitted by the human skin is
the frequency of the radiation is related to the wavelength by
where
is the speed of light. Plugging numbers into the formula, we find the frequency of the radiation:
2) The frequency of this radiation is 313 GHz, and its wavelength
. If we look at the table of the electromagnetic spectrum
https://en.wikipedia.org/wiki/Electromagnetic_spectrum
We see that we are in the range of visible light (in particular, in the infrared range).
Therefore, the correct answer is <span>2. visible light .</span>