1) The wavelength of the radiation emitted by the human skin is
[tex]\lambda=960 \mu m = 960 \cdot 10^{-6} m[/tex]
the frequency of the radiation is related to the wavelength by
[tex]f= \frac{c}{\lambda} [/tex]
where [tex]c=3 \cdot 10^8 m/s[/tex] is the speed of light. Plugging numbers into the formula, we find the frequency of the radiation:
[tex]f= \frac{3 \cdot 10^8 m/s}{960 \cdot 10^{-6}m}=3.13 \cdot 10^{11} Hz [/tex]
2) The frequency of this radiation is 313 GHz, and its wavelength [tex]960 \mu m[/tex]. 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 2. visible light .
