Why are humans not able to see,feel or hear radio waves? We are sensitive to the rest of the waves in the EM spectrum. If EM waves are composed of oscillating magnetic and electric fields, why am I not electrocuted by the electric constituent of the Radio waves?
In: Physics
op says we’re sensitive to other waves in the spectrum; my recollection is we only naturally use the visible? presumably, since they don’t help day to day life of hunter gatherers.
which would lead me to ask if there are animals that use the other waves day to day; think there’s sea life in the deeper parts of the ocean that do?
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Radio waves are made BY electricity in human tech, but are not made OF electricity. While a long range transmitter may need hundreds of watts of power, electrons are not radiating out from it.
Also, we SORTA do. Visible light is part of the electromagnetic spectrum and your eyes detect that, but it’s up in the terahertz frequency range where the waves tend to bounce off most things and frequencies are filtered differently by different materials which causes what we call “colours”. So there’s that.
Radio waves have wavelengths of several feet, so humans are virtually transparent to radio waves, like glass is transparent to visible light. If you have a piece of conductive metal the right length (an antenna), the waves WILL interact and make electricity move in it. Because the signal is so weak and humans are not as conductive as metal, we don’t notice any effect.
But if you stand really close to a powerful transmitting antenna, it can heat up your body (microwaves were discovered this way when a technician noticed the chocolate being melted in his pocket).
> We are sensitive to the rest of the waves in the EM spectrum.
Why do you think that? Humans can directly detect just visible light. This is is a very small frequency spectrum of 380 to 740 nanometers or 430–770 THz depending on if you look a wavelength and frequency. Anything above or below we can’t detect directly.
You can detect another part of the spectrum the way it heats you up, IR light will heat up the surface of the skin and you will feel the change in temperature. Radiowave can heat you up too and you can feel that. The difference is that they will penetrate you deeper and heat you up on the inside too.
If you were in a microwave oven you would feel it when it heated up your skin but at the same time, it would heat the inside of you and damages cells that are more temperature-sensitive then the skin and damage them.
It is not fundamentally different from how you damage your retina if you look directly at the sun but your skin is fine being exposed to direct sunlight. For radio and microwaves, you are quite transparent so they would heat up your retina just like your skin. The result is levels that damage your retina before you feel the heat on your skins. So for safety reasons, humans are not allowed to be in front of a radio or microwave transmitter that has enough power for you to feel it because it would be damaging you.
In terms of human evolution, sensitivity to radio waves (like a radio wave “eye”) doesn’t buy us much. They are much longer in wavelength than visible light, which means they can’t tell us about as many small details of the environment as light waves can. They have other benefits – going through solid structures for example, or very long ranges – but it turns out that for most animals, what’s in front of them is much more meaningful than whether there is a mountain on the other side of the forest or not.
As far as electrocution, they’re very low power. If you got up close to a high power antenna, you’d get burned.
The same reason ALL animals are not sensitive to them.
No animal is affected by radio waves, or uses them. Bats and dolphins etc. can use ultrasonic but those are miles away and totally different from what you know as radio waves.
There’s no animal that’s picking up AM radio. The construction of organic matter means that it isn’t sensitive to it, so it doesn’t even get utilised in the smallest way (unlike even magnetism from the Earth which is used by homing pigeons), even when the animal has no sight, hearing, etc.
It just doesn’t affect biological matter, because of the wavelengths involved. Where it *can* affect biological matter, you are sensitive to it – infrared as heat, colour as sight, etc.
It’s also *such* low power that even if there were a sensitivity, it would have to be extreme, or the powers necessary to make you notice it would fry you.
It’s one of the reasons that the whole “mobile phone is frying your brain” thing is largely nonsense.
As others have said, radio waves with enough power and proximity will heat our internal tissue which is considered dangerous. There is a maximum permissible exposure (MPE) that you can calculate based on frequency, power density, proximity, and duty cycle (how long the radio is transmitting for). Some more reading here: https://www.fcc.gov/general/radio-frequency-safety-0
As an example, many 5 watt VHF handheld transceivers used in amateur and marine radio technically exceed the MPE if you hold the radio up to your face while talking – even with a modest duty cycle. Thus, current recommendations suggest using an external mic with the radio.
Cellphones have a power density measured in milliwatts so even with a large duty cycle and close proximity they never get close to a humans MPE.
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