I get radiation is basically light…..some we some we don’t. And the more intense it is the worse it is. So if a thing has become radioactive, is it basically glowing? And how is that happening? What is the energy source?
In: Planetary Science
Not every radiation is light. Some are also particles being shot around.
The energy comes from instable atoms falling apart. There are immense forces holding the protons and neutrons in an atom together, and the instable ones are basically “unbalanced” and will randomly snap into a more balanced state. Imagine it like a mousetrap going off, releasing energy that was previously stored in a stretched spring.
There are four types of radiation:
* Electromagnetic radiation, or light. *All* objects emit light via **thermal radiation**, which is basically glowing from being hot. A red-hot pan is thermal radiation; you, too, emit thermal radiation, but it’s both dim and in the infrared part of the spectrum you cannot see (but infrared cameras can). There are also dangerous types of EM radiation, like x-rays and gamma rays. Light can be viewed as a wave; its frequency (speed of wiggling) denotes how much energy is in them. X-rays and gamma rays have a very high frequency, so they contain a lot of energy; enough to break apart molecules into ions. We call this **ionizing radiation** and it is dangerous because it can break apart your cells (causing burns) and damage DNA (causing cancer).
* Alpha radiation. Basically a helium nucleus (two protons and two neutrons), kicked off of a decomposing atom that’s too big to hold on to all its protons & neutrons. They’re slow and heavy and big, and thus can be stopped by a very thin barrier, but they contain a lot of energy and are ionizing as well.
* Beta radiation. Just a free electron traveling at high speeds. Also ionizing and dangerous, but highly interactive and so it gets stopped moderately easily. These free electrons get created by beta decay, when a neutron breaks apart into an electron, a proton, and an antineutrino (don’t worry about the antineutrino, it’s too weird to discuss in depth here)
* Free neutrons, flying very fast. These get kicked off of atoms when they decay. When they hit another atom, they can then cause *that* atom to decay and kick off its own neutrons. This chain reaction is what makes nuclear reactions either self-sustaining (as in a nuclear power plant) or take off out of control (as in a nuclear bomb). In a reactor, control rods (which are not radioactive, but do absorb or slow down neutrons) are used to make sure the reaction stays at a constant rate.
When something is “radioactive”, that means that the nuclei of the atoms in this substance are unstable. They either have too many or too few neutrons and thus the nuclei can’t stay together. A nucleus in that situation is going to undergo some kind of nuclear reaction to achieve stability, with the most common being radioactive decay. This is when bits and pieces of the nucleus are being spat out to get to that ideal combination of protons and neutrons. Those high energy particles are the most damaging type of ionizing radiation. They are alpha particles (two protons and two neutrons), beta particles (1 electron), and free neutrons. What you’re thinking of when you say “radiation is basically light” is electromagnetic radiation. That is also created in radioactive decay, called gamma radiation.
Radiation from radioactive materials is actually invisible. Even a very strongly radioactive material will just look like a piece of metal or mineral. You might be able to sense that something is strongly radioactive if it feels warm to the touch, or you develop skin burns just by standing near it – but in either case, this is a *very* bad situation for you and you should not be wherever you are right now. Mildly radioactive materials would be impossible to distinguish from non-radioactive materials.
There are two phenomenon that you might be thinking of here, though. One of them is due to the ionization of air. High energy can cause air molecules to ionize, basically losing their electrons and becoming plasma, for a brief time, and this causes them to emit light. This is the reason why lightning emits light – the electricity ionizes the air as it travels. Ionizing radiation can – as the name might imply – ionize materials like air, and under certain conditions this can be enough to make the air glow blue. Again, though, if you’re in a place seeing this happen, you should probably leave immediately; some of the few times it’s ever been seen is in the Chernobyl disaster, directly above the uncovered core immediately after the explosion, and during accidents like the ‘demon core’ incident that killed Louis Slotin.
The other phenomenon is Cherenkov radiation, which is again visible as blue light, but is produced by a different mechanism. It’s kind of complicated so I won’t go into it, but suffice to say that fast-moving particles in a medium (like water) can cause it. This one gets associated with radioactive materials because it is often visible in nuclear reactors.
Imagine a brick wall. Bricks are held together by mortar, so they form a single object. That’s an atom.
Now, take a brick wall that is much too big/high to hold together. Too many bricks sitting on not enough mortar; it is swaying in the wind and can come down any minute. This is an atom of a radioactive material.
Then, that wall finally falls down at a random moment. Bricks and mortar dust go flying everywhere. This atom just has undergone radioactive decay and everything that goes flying is what we call radioactivity.
The source of the energy was the energy that was used to put the wall up. The flying bricks, brick parts, dust, pieces of mortar, etc. are the different kinds of radiation. FivedozenWhales has given a very nice list of the types.
The bricks are alpha; they don’t fly very far or fast, can easily be caught with simple netting, but if they hit you, they really hurt. Pieces of bricks are neutrons; they go through nets, are quite fast, and when they hit another unstable wall, they have enough energy to bring it down. The dust is EM; it goes everywhere, nets do nothing against them, and while not the most energetic, you don’t want to get a lungful (or eyeful) of dust.
And yes, you can call something “glowing” when it emits EM radiation, but we usually restrict that word to mean “emitting visible light”. You wouldn’t describe a radio antenna as glowing because it emits radiation radio waves. Radio is just as invisible as X-rays and gamma to us; in fact, we can only see a very tiny part of the EM spectrum. For secondary effects, where radiation causes something to glow, see MercurianAspirations’s answer.
>I get radiation is basically light…
*Electromagnetic* radiation is more or less energetic light, but *nuclear radiation* includes massive particles like protons, neutrons and electrons. Anything with a temperature emits electromagnetic radiation (i.e. glows); radioactive materials aren’t just glowing, their atoms are decaying and casting off particles. The energy source is the energy that was binding those particles together and is released as they decay.
Atoms have energy and will release this energy under certain circumstances. With light elements like hydrogen and helium, it is possible to push these elements together to create new elements, this is called fusion energy and normally takes place in stars https://youtu.be/vVE0B6g9F_0 The heavier elements like Uranium and Plutonium can be split apart releasing energy this is called fission energy and this is the energy used in nuclear power stations and early nuclear weapons.
Anything that radiates is radiation. It’s only light if photons are being radiated.
Neutron radiation, for example, is not light.
Radiation is a broad term covering different things that share some qualities but don’t share other qualities.
Generally if you split radiation into two smaller categories: waves and particles the concept becomes clearer.
Wave radiation is things like light. Light comes from many sources including things you are familiar with such as fires. All wave radiation moves at the speed of light. It behaves like a wave (but also sometimes like a particle.)
Particle radiation is things like alpha particles which are two protons and two neutrons. It’s a particle, the same things you learned about in chemistry. It does not move at the speed of light. It does not behave like a wave.
Pretty different things right?
Now, there’s some relationship between wave radiation and particle radiation when it comes to nuclear material. Nuclear material is unstable and tends to break apart over time. Some types of nuclear material when it breaks apart it releases particles like alpha particles. Some types release waves like xrays.
Two different types of things being released by one type of thing: radioactive material. But just because humans release carbon dioxide and feces as waste products doesn’t nessecarily mean that carbon dioxide and feces are the same thing or that they behave in some unified manner. In fact, they behave quite differently in some qualities. The same holds for wave radiation and particle radiation.
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