Video: Harmful Effects of Radiation on Humans

Which of the following types of radiation sources is the most dangerous to ingest? [A] An alpha source [B] A beta source [C] A gamma source


Video Transcript

Which of the following types of radiation sources is the most dangerous to ingest? A) An alpha source, B) a beta source, C) a gamma source.

Okay, so in this question, we are trying to work out whether an alpha source, a beta source, or a gamma source is the most dangerous kind of radiation source to ingest or to absorb into the body. Most commonly done by swallowing it. So let’s go through each one of these sources one by one and try and work out the characteristics. Let’s start with an alpha source.

An alpha source is a source that emits alpha radiation. Well, alpha radiation is made up of alpha particles, which are also known as helium nuclei. Because they’re made up of two protons and two neutrons. Now, because alpha particles are made up of two protons and two neutrons, they are highly charged particles. Because, remember, protons are positively charged particles. And neutrons are not charged at all. Therefore, each alpha particle is carrying the charge of two protons. And this means that as the source emits an alpha particle, an alpha particle will very quickly bump into, let’s say, particles in the air. And it will steal electrons from these particles because remember electrons are negatively charged. And so the massive positive charge on alpha particles will attract electrons towards it. And this will leave the original air particles ionized, which means that those particles will have lost electrons.

Now because of the fact that alpha particles are so highly charged that they carry the charge of two protons. And because they’re so massive. Remember, they’re made up of two protons and two neutrons. Alpha particles cannot travel very far away from the source before stealing electrons from particles that they collide with. And once the alpha particle has stolen these electrons, specifically each alpha particle will steal two electrons. The alpha particle is no longer an alpha particle, but rather a helium atom. Because now they contain two protons, two neutrons, and two electrons. And so the charges on the two electrons balance the charges on the protons in the helium atom. But it does this at the expense of the particle that it collided with. It leaves the particle ionized. And it’s highly likely to ionize these pink particles that we’ve drawn here. Because, remember, the alpha particle has a charge of two protons. That’s quite a large charge. So to summarize, alpha particles can’t travel very far before they become helium atoms, rather than helium nuclei. But they very strongly ionize whatever they collide with.

If we instead look at the beta source though, it will emit beta radiation, which is basically electrons. Now, electrons will also meet particles in the air in this case, in the way that we’ve drawn it, and ionize them. Because, remember, electrons are charged particles. They are negatively charged. However, the size of the charge on one single beta particle or, in other words the magnitude of that charge, is only half the magnitude of charge on an alpha particle. Because, remember, protons and electrons have the same size or magnitude of charge. It will be opposite signs. And an alpha particle contains two protons whereas an electron is just a single electron.

So in terms of size of charge, an electron only has half the charge that an alpha particle has. And so beta particles are not quite as likely to ionize these pink particles that we’ve drawn here. And as a result of this as well as the fact that electrons are very small particles. Beta particles can actually travel a little bit further away from the source than alpha particles before they end up causing ionization. So in comparison, beta particles are not quite as ionizing as alpha particles. But they can penetrate the external environment such as air, a little bit more than alpha particles can.

Now if we look at a gamma source, a gamma source actually releases gamma rays, which are a type of electromagnetic radiation. Now, these gamma rays can indeed interact with the pink particles that we’re drawing here to represent air molecules. But remember that gamma rays, being electromagnetic radiation, are not charged particles. So the only way that gamma rays can interact with these pink particles is if these gamma rays, by virtue of their energy, can knock electrons out from the molecule that they happen to interact with. They, however, are not going to partake in any electrical interactions because, like we said earlier, they’re not charged.

And so although gamma rays can cause ionization, they’re a lot less likely to than beta particles and alpha particles. Because they don’t have any electrical charge or electrical attraction. Essentially, they just have to happen to collide with an electron in an atom in order to knock that electron out of the atom. And that’s how they ionize. So because gamma rays are not quite as ionizing, they can actually travel a lot further than alpha particles or beta particles. And hence, we say that they are more penetrating because they can penetrate further into, in this case, air.

Now based on all of this information regarding alpha sources, beta sources, and gamma sources, we need to figure out which one is the most dangerous to ingest. Well, outside the body, if we have an alpha source, a beta source, and a gamma source, because alpha particles are not very penetrating, they will probably ionize some parts of the skin. But they will not be able to penetrate the skin. Because they’re so ionizing and because they lose energy so quickly because they’re so massive. And hence going into the skin is quite difficult for them. The same is kind of true for beta particles although they’ll probably make it a little bit further into the skin. However, gamma rays can quite easily penetrate skin and go all the way into the body. Whilst at the same time not causing quite as much ionization as alpha particles and beta particles can.

So outside the body, alpha particles will cause the most damage but not go quite as far into the body. Beta particles are the middle case in this situation. And gamma rays will go furthest into the body but not ionize as much. However, if we’ve ingested all of these sources, then it’s a completely different story. Because when we’ve ingested these sources, they are already inside the body. And hence, at this point, the alpha particles can wreak most havoc because remember they’re the most ionizing. And they don’t even need to penetrate far in order to cause damage to the inside of the body. Whereas beta particles and gamma rays will also cause damage. But because they’re nowhere near as ionizing as alpha particles, they won’t cause nearly as much damage inside the body.

So overall, we can say that because alpha particles are so ionizing, ingesting them is the most dangerous. Because they can cause the most damage to the inside of a body once they are already there. And hence our answer to this question is that the type of radiation source that is the most dangerous to ingest is an alpha source.

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