Gamma-rays can go through a body but they will ionize a lot of atoms (I don't know whether some of the gamma photons will go through without any interaction at all?). The same for X-rays. Visible light and infrared (till $1mm$) probably only reflects and absorbs. But perhaps rays from 1 cm and longer (radiowaves) can get through the human body without harming the body or without changing in frequency?

  • $\begingroup$ Penetration depth decreases with increasing frequency. Here is a PhD thesis on the subject. $\endgroup$ – lemon Feb 24 '16 at 11:03
  • $\begingroup$ Your microwave oven has a frequency of approx. 2.4GHz and a wavelength of approx. 12cm and that wavelength will definitely get absorbed by your body really well. There are national and international em radiation limits at basically all frequencies almost all the way to DC and with good reason. The human body does absorb and will be affected at essentially all frequencies. $\endgroup$ – CuriousOne Feb 24 '16 at 11:06

There are two effects of electromagnetic waves on human body.

  1. Heating effects, occurring mostly around 2.45 GHz (which is the frequency used in microwave ovens)
  2. Ionizing effects, which can damage human body and cells

Here is a picture of how the radiowaves penetrate the human body according to the frequency. The legend is from 1 to 10 : Cosmic rays, gamma rays, X-rays, ultraviolet, visible spectrum, infrared, microwaves, radiowaves, very low frequencies, extremely low frequencies.

enter image description here

  • $\begingroup$ How do I have to interpret the arrows? $\endgroup$ – Marijn Feb 24 '16 at 11:28
  • $\begingroup$ It gives the approximate length of how much the radiowave penetrates the human body at this frequency. e.g. all waves below 100 Mhz get through while light and infrared do not (of course) $\endgroup$ – MaximGi Feb 24 '16 at 13:15
  • $\begingroup$ you do not give a link of the source for the plot $\endgroup$ – anna v Feb 26 '17 at 11:54

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