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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Light is an EM wave. It’s energy is proportional to its wavelength. And so thats all we need to care about.
Lets start with something called Compton scattering. We look at a free electron (free in that it isn’t bounded to an atom) and light comes around. The electron is negatively charged so it changes the EM filed around itself and this will affect light. Mathematically we can instead treat both light and the electron as little balls that collide. Calculate their momenta and see how light is deflected. The surprising thing is that the scattered light loses energy, it moves the electron. More energy, bigger kick.
We often model an atom’s electrons as they are bound to the nucleus with springs. We call this a harmonic potential, system with that tend to sit in some potential valley. If you kick them a bit they’ll return to their original state. Like a ball in a bowl. Electrons in their orbitals can be modeled much the same way. So lets play with the analogy:
If light comes around and scatters from this spring attached electron it will make it oscillate a bit. There are a lot of ways model whats going on. You can use the E field component of the EM wave and see how it moves the charges in the atom but this ball model works well for what we are interested in. There is same critical kick the electron can get above which it’ll leave the atom and fly off to infinity. If your light has enough energy for that, to knock electron from their orbitals we call that ionising radiation.
Why is that bad for us? Our cells are made of proteins, complex molecules. And if we knock electrons from their orbitals we break the bonds that keep molecules together. So proteins break down, if too much the cell just dies. But proteins are always made by the cell from a blueprint we call DNA. That is another complex collection of molecules and that can get damaged much the same way. So the cell won’t be able to produce the right proteins and dies. Or its slightly altered but still function just not cooperating with other cells. If this useless cell starts coping itself it’ll grow into a tumor. Our immune system does a good job at getting rid of tumors but occasionally it’ll fail and the tumor can graduate into being cancer. If too much DNA is damaged in too many cells these cells and their copies won’t be functional and now we are talking organ damage on a cellular level. This is decomposition. If new health cells don’t form you decompose. This condition is acute radiation poisoning. The mechanism that ends up killing you is similar to getting shot to cheese. It’s just that bullets damage your organs on macroscopic scales. If some vital organ get too many holes it’ll stop functioning and you die. Accompanied by internal bleeding, it’s just that bullets mechanically tear holes into you blood vessels while the decomposition allows for holes to form on your blood vessels.
So the cause of death after radiation poisoning is organ damage and internal bleeding. And the reason is you accumulating so much DNA damage as radiation breaks your molecules that cells stop functioning and you don’t have enough healthy cells to replace all the faulty ones.
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