As I understand it, the only real difference between radio, visible light, x-ray and everything in between is its wavelength. For instancew, radio has a very long wavelength, x-ray very short, visible in the middle somewhere. This means that radio can penetrate stuff (matter?) more effectively, among other things.
Radio waves are (essentially?) harmless, but shorter wavelengths are famously more dangerous, from sunburn all the way to straight up cancer and so forth. Why is that?
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Radio/light/x-ray/gamma-ray is all made up out of the same thing: photons.
The photons differ in only one way that matters for this, their wavelength/frequency/energy.
Wavelength, frequency and energy may all appear to measure different things but they are all the same thing as far as photons are concerned. If you know the wavelength of a photon you also know its frequency and how much energy it carries.
The shorter the wavelength the more energy each individual photon carries.
Each individual photon has a set amount of energy that it carries that corresponds to its wavelength.
Blue photons carry more energy than red ones for example.
You can make up for that by simply sending more photons of course.
If a photon carries half as much energy you can send twice as many photons and end up transferring the same amount of energy.
This is true for most things. But for some things the individual photon matters.
When a photon with enough energy hits a molecule or atom it might be able to knock an electron out of it. There is a hard minimum limit for that and you can’t get the same effect by hitting and atom wit two smaller photons as with one big one.
This knocking out an electron is called ionization.
Radiation where the photons have enough energy to do that is called ionizing radiation.
Because removing the electron means that the atom that remains is missing an electron and now charged.
Charge molecules want to get back to neutral again and may end up stealing an electron from some other nearby molecule.
Since electrons are what keeps atoms together in molecules this ionization will mess up with molecules and their chemistry.
The building plan of our bodies DNA, is a giant molecule.
Shooting ionizing radiation at it or having it be exposed to ions is like shooting a gun at a blueprint for a house.
Most of the times the holes you cause won’t matter much and there are all sorts of fail-saves and redundancies to keep your body from building stuff from corrupt plans, but if you shoot enough holes at enough plans for long enough you may end up getting unlucky and end up with a situation where the plan is damaged in such a way that your body ends up build cancer cells instead of healthy ones. This can be bad for your health.
Of course this does not mean that photons with lower energy are completely harmless.
For example microwaves are not ionizing, but they can hit water molecules just right to heat them up. since humans are mostly made up out of water and die if they are cooked. Being microwaved can be quite bad for you.
Also if you are hit with enough photons at once it doesn’t really matter whether they are ionizing or what wavelength they are.
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