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Wireless devices operating on electromagnetic waves have become indispensable part of our daily lives. At the same time, it also raises concerns about ill effects of such radiations on human body. That is why radiation power of wireless devices and masts are regulated. My question is following. Is higher frequency electromagnetic radiation more harmful for human body than lower frequency radiation, everything else being same? While this question lies in the domain of biology, I am looking for physics' perspective on this matter.

Edit1: please limit the discussion to radio waves as I am taking about harms of radiation pollution by wireless devices. X rays and the ilk are already notorious for their effects.

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    $\begingroup$ Neither studies, nor known physical phenomena, indicate health damage in humans for RF radiation such as 'wireless devices' generate, unless we're talking about heating effects. $\endgroup$ – Whit3rd Nov 17 '16 at 10:26
  • $\begingroup$ @Whit3rd is heating effect not a health effect? $\endgroup$ – akm Nov 17 '16 at 10:29
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    $\begingroup$ Heating (RF burns from being close to a high-energy antenna) has no real dependence on frequency. $\endgroup$ – Whit3rd Nov 17 '16 at 10:35
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    $\begingroup$ @AmitMaurya: A mobile phone transmits a few watts, of which some small amount ends up heating your head. If you ever go outside, the Sun dumps at least a hundred times this heat in your head. If you worry about the heading effect don't ever go outside. $\endgroup$ – tfb Nov 17 '16 at 11:41
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    $\begingroup$ What do you mean by "physics' perspective" here? This seems to be a pretty clear biology/medicine question: Whether radiation is harmful or not to humans. What is harmful to organisms is biology/medicine, so what exactly do you want to know from the "physics' perspective"? $\endgroup$ – ACuriousMind Nov 17 '16 at 13:51
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According to quantum mechanics, the electromagnetic radiation is quantized. This mean that it travels in "packets" called quanta. The size of this packet is proportional to the frequency of radiation, higher frequency radiation is carried in larger packets.

So the power delivered by a low frequency radiation comes in a great number of small packets, while the same amount of power carried by an higher frequency radiations is composed by few large packets.

This is the reason why high frequency radiation is more harmful than lower frequency radiation.

If you are irradiated by a low frequency wave is like to be hitted by a great number table tenis ball while an high frequency wave is like be hit by very few bullets.

In particular, high frequency radiation has a ionizing power, which means is able to remove electrons for atoms and eventually damege biological structures like the DNA. Moreover, as the frequency get higher the penetration power of the radiation increase which means that damage can be affect deeper parts of tissues.

Obviously you have to define which is the frequency where harmful effects began to appear. In general, UV light can cause superficial damage (which can however be quite dangerous because skin cancer is a superficial damage, too). Xrays and gamma rays are very dangerous and can cause terrible damage to biological structures.

As far as I know, there are no scientific evidence of damage caused by radiation which frequency is below the visible light.

Obviously the one I described is only the main mechanism of interaction, but is not the only one. Microwaves, for example, are not dangerous in general, but as you can see every time you use your oven, using a specific frequency can cause effect like heating which eventually can cause damage.

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  • $\begingroup$ please see the edit. $\endgroup$ – akm Nov 17 '16 at 10:49
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You've probably heard of infrared light (IR) and ultraviolet light (UV). We're often told of the damaging effects of UV light from the sun which is why we wear sun-block, but you don't hear anything about IR being damaging to human health. The only difference between these two forms of light is the colour (or frequency).

You're right that the higher frequency radiation is more harmful. This follows as a result of the formula

$$E=hf$$

Where $E$ is the total energy of a particle of radiation, $h$ is Plank's constant, and $f$ is the frequency of the wave.

From this formula we see that higher frequency radiation has more energy contained in it which has more potential to disrupt processes in the body. How exactly the energy of radiation leads to damage in the body is more to do with biology than physics.

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    $\begingroup$ The 'higher frequency is more harmful' conclusion only applies to the ionizing radiation range of the EM spectrum, and not the RF range that was originally mentioned. $\endgroup$ – Whit3rd Nov 17 '16 at 10:38
  • $\begingroup$ @Hugh please see the edit $\endgroup$ – akm Nov 17 '16 at 10:49
  • $\begingroup$ @AmitMaurya There's nothing different about the physics for radio waves compared to Xrays. Clearly the energy in higher frequency radio waves is higher than that of low frequency radio waves. The higher frequency waves have more potential for damage but as Whit3rd's comment suggests the levels of energy in any radio waves may not be harmful for humans, this is a medical detail not a physical detail. That is, the higher energy may not be of any practical significance. $\endgroup$ – Hugh Nov 17 '16 at 11:28
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No one is bringing up the idea of power or amplitude into this discussion. I found page while researching a question someone had about a Microwave oven operating at roughly the same frequency (2.4gHz) as a cell phone on 4G system. My research so far has indicated alignment with my intution that that microwave oven operates at a much higher POWER than the cell phone. Oven is operating at 1100 watts (120v). Cell phone is operating at 27 dBm or 500milliwatts (https://en.wikipedia.org/wiki/DBm).

So, I am answering this question with yet another question.

How is power/Amplitute/intensity related or measured for very high frequencies?

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The kinds of harm EM radiation in the kHz - GHz range may cause to people is not purely a physics question, but very much also a biology/medicine question.

However, one particular kind of harm, the heating effect, is well known to physicists and engineers. It cannot be said that given fixed electric field amplitude of plane wave, in general higher frequency radiation has greater heating effect than lower frequency radiation; there are ranges of frequency where the heating is more efficient.

The heating efficiency of radiation on a given human body depends on radiation frequency, body parts sizes and also on the environment where the body is located, such as distance from the ground, conductivity of the ground, etc. [1]

[1] http://www.arrl.org/rf-radiation-and-electromagnetic-field-safety

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