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Asked by to Clara, Simon, Thomas on 20 Mar 2014. This question was also asked by .
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Simon Albright answered on 20 Mar 2014:
That mainly depends on the type of radiation.
The three main types are Alpha, Beta and Gamma but you also get neutrons produced naturally (though far less often).
Alpha particles are helium nuclei and as radiation goes they’re the beef cakes. When an alpha particle interacts it smashes into everything in it’s path leaving a trail of destruction but also stops really quickly. They lose energy so fast a sheet of paper is enough to stop them.
Beta particles are super fast electrons. They go much further than alpha particles and don’t do as much damage on the way. You need a little bit of metal to stop beta particles.
Gammas are high energy photons (particles of light). These very rarely interact which is both good and bad. It means that if a little gamma radiation goes through you it won’t do much BUT it means it’s really hard to stop. You need at least a block of lead to stop gammas and the really high energy ones need more than that.
Neutrons are the odd one out. Neutrons behave weirdly and you’re better off putting a block of polythene (what they make carrier bags out of) in the way than a block of lead. The big problem with neutrons is that they make things radioactive so you have to make sure you know how many there are and what they interact with.
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Thomas Elias Cocolios answered on 20 Mar 2014:
Radioactivity does a lot, but there are actually many ways to answer that question.
First of all, radioactivity is the process by which an unstable nucleus decays back closer to stability, and then further until it becomes stable. It comes from the fact that the strong force which binds the nucleons (protons & neutrons) together works best when you have the right balance (as many of each, slightly offset by the fact that protons are positively charged and repel each other). There are several ways to decay: alpha, beta, gamma.
Alpha decay is the emission of a helium nucleus, made of 2 protons and 2 neutrons. It is actually the most efficient way for a nucleus to release energy, but it releases so much of it that is not the most common process of them all. Considering how energetic it is, though, it was the first to be discovered. It is found mostly in heavy isotopes (e.g. polonium, my favourite).
Beta decay is the transformation of a neutron to a proton, or vice versa, to restore the balance. It is called a ‘weak’ process (by opposition of the strong force) but is the most commonly found. In order to restore charge balance, it is accompanied by the emission of an electron or positron (the anti-electron) and, to restore particle type conservation, a neutrino.
Gamma decay is the emission of high-energy photon to allow an excited atom to decay to its fundamental state without changing its nature. This is the last form of radiation and mostly follows the other two (we then talk about alpha-gamma, or beta-gamma).
As to what each of those radiations do, it is then a question of how massive and energetic the particles are. Alpha are very heavy (4 nucleons) and therefore stop very quickly when they interact with matter. Electrons are ~8,000 times lighter and will progress further but leave less energy altogether. Finally, the gamma penetrate very far and leave a lot in their wake, but overall less as well.
The process by which those radiations affect materials (and your body) is called ionisation. By slowing down and stopping, it ionises its surrounding and, e.g. in cells, breaks down molecules. Since the alpha particle leaves a lot of energy in small space, it completely destroys a cell. On the other hand, they can be stopped with a sheet of paper, while gammas can penetrate through meters of concrete, so quite hard to shield yourself from them.
Beyond that, radioactivity can be used for many application. In nuclear energy, we use the vast amount of energy released in fission as heat to boil water and make an engine turn. In medicine, we use the high penetration power of gammas for imaging, and the high destructive power of alphas for cancer treatment.
If you have more ideas, there are many ways to get involved in this research and a lot promises!
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Clara Nellist answered on 21 Mar 2014:
To expand on what the others have said about radiation: It can be very useful in medical applications! Specifically, something that links to my research is a medical procedure for cancer patients called hadron therapy (Thomas mentioned it briefly in his post).
A hadron is just a name for a particle that is made up of three quarks and held together by the strong force. Common hadrons are protons and neutrons. In the case of hadron therapy, we’re also talking about bunches of hadrons like the nucleus of an atom (the protons and neutrons without the electrons on the outside). The reason they’re so great for this kind of treatment is that the energy that these particles deposit in a person (and so causing the damage) is almost all at the end of the particle’s path. For lighter particles, like electrons or photons (gamma rays), the damage is spread out over the whole path. This is important because we only want to damage the cancer tumour and not the healthy tissue around it.
To get the hadrons to the energy that we need, we use a particle accelerator. This is the same principle as the Large Hadron Collider, but on a much smaller scale (about the size of a large room).
The energy of the particle is important because it will decide what distance in the body the damage will be done. If we can focus this damage onto just the cancer, and rotate the beam around the patient, then we can kill the cancer and not expose too much of the the rest of the patient to excess radiation.
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