Types of Radiation

At the end of the 1800s, physicists were staggered to find there was radiation coming out of all kinds of things—just dirt and rocks. Uh, the very first time this was discovered was with a jar of uranium salts that was left in a drawer overnight, and in the morning, uh, a photographic plate that was next to it had been exposed, even though it had been in the dark all night. So where had the radiation come from? From this stuff, uranium salt.

It was so to discover that dirt was giving out radiation. There was worse in store; they discovered that there were three different types of radiation going on. Uh, so they really had no idea what was happening. Um, so what do you do as a scientist? You name it. So they named it Alpha, Beta, and Gamma radiation. Well, that's a bit dull, really, isn't it? So maybe let's go for something more sciency: Alpha, Beta, Gamma. Yeah, that's much better.

And I've got an example here. I've got, uh, some Alpha, Beta, and Gamma radiation sources here. I also have a Geiger counter, which is, uh, a little device that gives off a click when it detects radiation. So I can hold it over the source; you can hear you get a lot of clicks. So what are the different types?

So our Alpha radiation, it turned out, is pretty much completely blocked by paper, whereas the Beta and the Gamma make basically no difference. So if we try lead, our Alphas are completely blocked. Strontium—the Beta is pretty much blocked—but our Gamma source, it makes basically no difference. So we can even go to a thick solid piece of lead, and you can still see some things are getting through there.

Um, so we could try. There's a bit penetrating through. But I think I must be thicker than lead. So what are our three types of radiation? Scientists eventually worked out that the Alpha radiation is matter; it's two protons, two neutrons—that's the nucleus of helium. The Beta source gives out electrons, and the Gamma source gives out electromagnetic radiation.