Understanding and Detecting Radiation

And I want to define terms like radiation and radioactivity, to talk about the different types of radiation there are, and to differentiate between ionizing and non ionizing radiation and chat about the technology around it. So first, what is radiation. Well, it's a fairly broad term with lots of different meanings as it turns out, but I think that's part of why there's frequently a lot of confusion around the concept

of radiation. But there are a couple of definitions that for our purpose as we want to focus on, and really the one that we're truly interested in is the process of admitting radiant energy in the form of waves or particles as a definition I took from the Miriam Webster Dictionary. By the way, so radiation can involve electromagnetic waves or it might involve sub atomic particles. Uh, some radiation has the potential to be harmful, even deadly in

sufficient intensities and length of exposure. Some radiation is relatively safe, particularly under specific controls. So let's start with some early discoveries of electro magnetic radiation, as those predate our understanding of particle based radiation. So our story begins in eighteen

hundred with an early scientist named William Herschel. And Willie was interested in learning more about the spectrum of light, and it was already understood that if you were to pass light through a prism, you could separate light into different colors. You know, the good old roy g BIV spectrum, which stands for red, orange, yellow, green, blue, indigo, and violet.

The spectrum will always be in that order. Anytime you pass light through a prism, it's going to break into those bands in that order, and those bands actually represent bands of frequencies of light waves. Herschel was wondering if the different colors of light produced different amounts of heat, So is one type of light warmer than another, So he set up a system in which he positioned thermometers at each color displayed from light passing through a prism.

So he sets up a prism in his window, lights coming through it, and it's hitting a table, and it divides up into different bands of color. He sets the thermometers in each band of color, and he happened to have an extra thermometer just beyond the red end of the spectrum, so it's actually in the dark. It was beyond the range of the visible light. He had no way of knowing it, but he had, by happy coincidence,

placed a thermometer right where the infrared band was. And we can't see infrared light, but that light does transmit heat. In fact, Herschel was surprised to see that it was that thermometer, the one that was in the darkness, just beyond the red range, that actually registered the highest temperature out of all the thermometers he had set out. And we often talked about heat radiating outward from a source. In eighteen o one, another big thinker named Johann Wilhelm

Ritter built upon Herschel's experiment. He decided to see if perhaps there was anything beyond the other end of the spectrum, a k a. The violet end. In fact, he really discovered it sort of by accident. Ritter experimented by using a substance called silver chloride, and this is a chemical that turns black if it's exposed to sunlight. Ritter built on the understanding that blue light would produce a greater reaction in silver chloride than red light, so he did

a variation on Herschel's experiment. He again used a prism to break the light into bands of color, and then within each band of color he placed a vile a silver chloride to see if the reactions were different across the spectrum of light. He could see that, indeed, the reaction did vary across the spectrum. The closer you got to the violet side of the spectrum, the more intense the reaction was, and it was most evident just beyond the violet side, in an area where there was no

visible light at all. So clearly there was something going on on that end of the spectrum. So on the red end you were getting some sort of heat which we now know is infrared, and on the violet end there's something else that was really reacting to silver chloride. So Ritter would call this chemical raise, which to this very day we don't do anymore. Now today we call

it ultraviolet light. Herschel and Ritter had made the first steps to increase our understanding of the electromagnetic spectrum, of which visible light is just one tiny part, and as we would build on that understanding, we'd also gain more information about what effects these types of radiation can have on us. Some of them have very little effect on us, some of them can have a drastic effect on us.

And it would take a lot more time, but we would gradually begin to understand that if you look at the spectrum, it includes everything from radio waves on one extreme end of it to gamma raise on the other end of it, and these waves vary in wavelength, frequency, and energy. So on one extreme end you've got those radio waves. These can have really long wavelengths, measuring hens of miles, like sixty two miles or a hundred kilometers

for wavelengths of certain radio frequencies. So if you had a perfectly steady radio wave, like just imagine, it's a perfect signal you. If you were to map it out, it would be a beautiful sign wave. If you measured from the peak at one point to the next peak, that's the wavelength. That's what would have been a hundred

kilometers in distance an enormous wave. The frequency of a wave refers to how frequently a specific point on a wavelength, you know, like that peak, how frequently you could see that point on each wave pass a given reference point within a second. So with the longest radio waves at the lowest frequencies, you're talking about a frequency of around three thousand cycles per second, meaning that in one seconds time,

three thousand peaks past that given point of reference. Now, one thing to keep in mind is that this is electromagnetic radiation. An electromagnetic radiation all travels at the same speed, that being the speed of light. Now, we do have to remember the speed of light isn't a constant across all media. It's a constant within each media. So we we usually when we're talking about the speed of light,

we're talking about within the vacuum of space. But if light is traveling through an atmosphere or through water or something, it actually does travel at a different speed than that because it it's all dependent upon the medium. Still, electromagnetic radiation travels at that speed. So a wavelength of uh, you know, one wavelength of of a radio wave is traveling at the speed of light, as is one wavelength

of gamma radiation. However, because the radio waves are so long and the gamma rays are so short in wavelength, the frequency has to be different, right. The frequency of the radio waves has to be lower than the frequency of gamma rays because you get way more gamma rays passing within a frame of a second, even though they're both traveling at the same speed. All right, That gets confusing, right,

So I like to explain this with an analogy. Imagine you've got two identical straight roads, one lane wide, and they're right next to each other. Down one road, you have a series of buses, and each bus super long, measures eighteen meters in length, traveling down the road at fifty KOs per hour, and there's one meter of space in between each bus. So bus number one eighteen meters long than you have a meter, and a bus number two is eighteen meters long than you have a meter.

That's dangerous, but whatever, they're traveling down at fifty an hour, perfectly in sync with each other. On the other road, do you have a series of zippy little smart cars and each smart car measures just three meters in length. They're also going down the road at fifty kilometers per hour with a meter of space in between each pair of cars. Now, individual vehicles are all traveling at the same speed, they're all traveling at fifty kilometers per hour.

But the smart cars aren't as long as the buses. So if you were to have a accounter, there's someone standing by the bus lane and there's someone standing by the smart car lane, and they're holding a little counter in their hands. The person next to the smart cars is going to count way more smart cars in the same amount of time as the person counting the buses. And it's not because smart cars are traveling faster. They're not. They're just smaller, so more of them can go by

within that given amount of time. The same thing is true with wavelengths of the electromagnetic spectrum red light, blue light, X rays, radio waves. They're all traveling at the same speed. They just have different wavelengths, so they have to have different frequencies. Now, as I said earlier, in those early days in the nineteenth century, we didn't have this level

of understanding. We weren't aware of different wavelengths and frequencies, and we didn't know that longer wavelengths and lower frequencies of electromagnetic radiation carry less energy, whereas high frequencies and very small wavelengths of electromagnetic radiation can pack way more energy. If you were to look at the experiments of Herschel and Ritter, you might actually think that that's not the case, because the invisible light off the red end of the

spectrum was carrying a lot of heat. It was heating up a thermometer more than the others, so maybe it carries more energy. And whereas the violet side you just saw silver chloride change color. So it would take a lot more experimentation to get a deeper understanding of the

actual nature of electromagnetic radiation. Now to go into the full history of how that understanding would unfold is the stuff of college lecture series, So I'll just give very brief summaries to get us kind of closer to our objective. In the nineteenth century you had numerous scientists and inventors who were observing all sorts of interesting stuff that would later become integrated into our knowledge of electromagnetism. So Michael Faraday did a great deal of work exploring the relationship

between electric and magnetic fields. For example, his work would inspire a Scottish physicist named James Clerk Maxwell to look into the matter further, and Maxwell made predictions about electromagnetic radiation based on those early experiments and observation, saying, well, based on what we know, I expect that will eventually find something that fits this mathematical uh example of what should be there, and his predictions proved to be accurate,

and they in turn would serve as an important foundation for Albert Einstein's special theory of relativity, as the one that gives us the famous equation equals mc squared, which tells us that energy and mass are related at an intrinsic level. And Maxwell's observations about electromagnetic radiation would lead to a theory about heat radiation that in turn would be overturned by Max Planck, whose formulation of quantum hypothesis to describe how heat radiates would become the predominant one.

But all of that is a little outside of our scope. So the point I wanted to make is that the nineteenth century was a boom time for scientific observations and discoveries, and the things we would learn would serve us well as we moved into the next phase of understanding of radiation. And what it's all about. So the other big discoveries that relate to this episode came about at the end of the nineteenth century, so we get to look at

both ends of the eighteen hundreds. In eight Vilhelm runjeon which I mentioned him in the last episode, he was experimenting with a cathode ray tube, and I talked about that again in the Smoke Detective episode. Essentially, these are devices that produce streams of electrons by heating up a filament inside a glass vacuum tube, kind of similar to

a light bulb. Runjen found that as he applied an electric voltage to the cathode ray tube a light detection screen in his lab that was made out of barium platina cyanide fluorest, it actually lit up. It detected light

even though there was no visible light there. So he began to experiment with this phenomenon, this invisible light that was causing this this detector to light up, and that included putting objects between the cathode ray tube and the screen, and he saw that whatever was coming out of the tube seemed to be penetrating through objects and it was

still hitting the screen on the other side. He found that if he put photographic film, the energy would interact with the photographic film, and if you put something in between the film and the cathode ray tube, he could get a really interesting image of it. Uh, it's like you could see through certain stuff pretty clearly. So, for example, his hand, he put his hand in front of it and he took a photo. Then the picture would show

the skeleton in hand. It would it would show through the soft tissues of his hand, and he thought, well, this is interesting. He discovered a new type of radiation and he called it the X ray because what the heck was going to call it? It was an unknown quantity, and in mathematics we often refer to unknown quantities as X, like solve for X. So it was meant to be a placeholder. X rays just it turned into the permanent

name for the stuff. Now. Initially, no one was aware that X ray radiation was potentially dangerous with its shorter wavelength and higher frequency and energy than visible light. In fact, no one was even sure that was another form of light. They thought it might be, but they weren't certain, and that wouldn't be proven until nineteen twelve. But people began to understand that there was some potential danger the X

rays fairly early on. In eighteen nineties six, the year after Runton's UH discovery, the journal Nature published an article with the title The Harmful Effects of X rays. And in that article there was a story about a guy who had worked as an X ray demonstrator in London, and he described the effects of X ray exposure that he experienced, particularly on his hands, after working for a full summer doing demonstrations with X ray machines for several

hours a day, I'm going to quote an excerpt. In the first two or three weeks, I felt no inconvenience, but after a while appeared on the fingers of my right hand many dark spots which pierced under the skin, and gradually they became very painful. The rest of the skin was red and strongly inflamed. My hand was so bad that I was constantly forced to bathe it in

very cold water. An ointment momentarily on the pain. But the epidermist had dried up, had become hard and yellow like parchment, and completely insensible, so I was not surprised when my hand began to peel. From that point, the guy goes on to describe how things got even worse, like he began to lose fingernails and stuff. But I'm gonna leave out the rest of the grizzly details. The point is people are starting to notice that the longer someone was exposed to X rays, the more severe the

consequences seemed to be. Short exposures did not appear to be as serious, but this was something that people were starting to get a little concerned about that would grow in the years to come. But first, let's take a quick break before we jump into that discussion. Okay, so before we took our break, I was talking about how people were beginning to understand that X rays could be dangerous. That didn't stop early irresponsible implementations of X ray machines. However,

people thought of these as curiosities. They were things to be celebrated and experienced. Thomas Edison thought everyone would have one in their own home and thought perhaps they should have them, because again, they didn't understand the dangers yet. People would even have X ray parties in which guests would take X ray photos of themselves, you know, of their foot, or their hand, or even their face, and they would get to keep the photographs at the end

of the party. Shoe stores installed X ray fluoroscopes to get a look at a person's foot, And while a person visiting the store wouldn't likely walk away with a lethal dose of radiation, the folks who were working at the store were exposed to X rays much more frequently and for longer durations, and many of them would suffer the consequences. But all of those awful discoveries would take

some times, so people didn't immediately notice the issues. Meanwhile, let's get back to the discovery of radioactivity by talking about the other kind of radiation, not the electro magnetic type. So in eighteen ninety six, which was that same year that the Nature article about the dangers of X rays came out, there was a physicist named al Marie Beccarel who was wondering if some materials he was working with might produce the same sort of energy that Rundgen's X

rays seemed to create. One of those materials that Beckerel was working with was a crystal made up of uranium salts. Now, the various materials Beccarel had interest in all shared a common trait. They were all phosphorescent, so they could all glow, and he wondered if they were giving off the same sort of invisible light stuff that run Gen was observing with X rays. So Beckarel set up an experiment. He

put down a photographic plate. He totally covered it so that one of it would be exposed to light because that would activate the photoreactive chemicals on the plate. And on top of the covering he put a selection of his phosphorescent crystals to see if any of them would interact with the photo reactive chemicals. And he exposed the whole thing to the sun, you know, thinking that the

sun would charge these various crystals. And at the end of the experiment he discovered that out of all the different things he was testing, only one seemed to have any effect at all, and that was the rock crystal that was actually made up of uranium salt, and that was the only one that seemed to have fogged up the the photoplate. So he thought, well, I'll do a longer test. I'll leave it out in the sun longer, see if I get a bigger, more clear result. But

the weather at that point wasn't cooperating. It had gotten cloudy, so he couldn't put it out in the sun. So he takes his photographic plates and his uranium salts and he stores them away and waits for the weather to get better. So they were actually stored next to each

other in a dark cabinet. Several days later, as the weather was starting to finally clear out, he was getting ready to conduct his experiment, but he decided, you know what, before I do this, I better make sure these photographic plates are still good, because the chemicals can actually expire, and I'd be wasting my time if they aren't working anymore. So he picks one and develops it, and it happened to be one that was close to the iranium salts.

Rock He was surprised to discover that the bits of the photographic plate that had been close to those uranium salts had images on them, even though the salts had not been exposed to sunlight. They've been stored in a dark cupboard, and he concluded that the uranium salts themselves were giving off some sort of emission that was being captured on this photographic plate. Henri Becarel had a couple

of enterprising and brilliant assistants. One was Pierre Curie and the other was Marie Sklodowska, who would marry Pierre and become Marie Curie. She uh really was fascinated by radioactivity, and together with her husband, they began to study the ranium salts as well as looking for other similar materials that seemed to display this radioactive phenomena. They tested some

mining operation waste. It's called a pitch blend. The mining operations were happy to get rid of it because it was just run off from their operations, and they found that it could contained traces of radioactive material, and eventually they were able to separate a small amount of it from the rest of the pitch blend, and it would later be called radium. It was far more radioactive than

the uranium salts they had already worked with. The Curies and Beckrel would receive the Nobel Prize in Physics for their discoveries. Runen also received one earlier for his discovery of X rays, and then Pierre Curie would later tragically die in a traffic accident. Marie would go on to discover another radioact development, this one called polonium, and she would receive a second Nobel Prize, though that second one was in chemistry. She's one of only a few people

who have ever received more than one Nobel Prize. Now, one thing Beckerel did with his own research was proved that the energy coming out of this uranium salt was not the same thing as X rays, and he did this by testing the uranium salts against X rays with a device that could generate a magnetic field. So X rays would pass through the magnetic field unimpeded. And that's because X ray radiation has no electric charge, and thus it has no magnetic field of its own, so it's

not affected by magnetic field. It just passes through. Is that there's nothing else there but the radiation coming from the uranium salts bent upon encountering the magnetic field, and that told Beckarel that whatever was coming out of the uranium salts had an electric charge to it, because it had to have an electric charge in or to have its own magnetic field and thus be either attracted or

repelled by the magnetic field and his testing vice. So Beckerel tested numerous types of radioactive substances using this approach and observed three basic results. Either radiation would bend one way using certain radioactive materials, and he would conclude, this is a positive radiation material because it is being attracted to the negative side of the magnetic field and repelled by the positive side, or it would bend the other way,

so he would have the opposite conclusion. Okay, this is negative radiation because it's being attracted to the positive side and repelled by the negative side, or it passed straight through like X rays, and it would have no electrical charge at all, so it would be neutral. So you

had positive, negative, and electrically neutral radiation. In their work, the Curies and Beckarel noted that prolonged exposure to some of these radioactive materials would result in injuries and ailments, like if you handled some of the more radioactive stuff like radium for any length of time, you could actually get burns on your skin, and you could suffer radiation sickness, which includes symptoms like nausea, but the extent of the

damage was unknown for years. Marie cry died in nineteen thirty four of a plastic anemia, which was probably a consequence of her exposure to radioactive material over the years. It certainly would have increased the odds of her developing that, and that's something that is is good to just mention in general is that when we think of radiation, we often think of the radiation sickness, the sort of acute symptoms you can have if you have a sudden exposure

to an intense amount of radiation. But in many ways, the consequences of exposure to radiation are really more about the increased risk of developing UH conditions like cancer. UH. And it doesn't necessarily mean that if you do develop cancer, that it was a direct result of that exposure to radiation, but rather or that the exposure to radiation increased the

odds that you would develop cancer. It's a complicated thing to look at because without knowing all the variables, you cannot say conclusively that X caused why, but you can't say that X made Y way more likely. That's what we think with Currie, that she probably developed a plastic anemia as a consequence of this exposure to stuff like radium over the years. Many of her belongings and even a cookbook she used, are actually stored in shielded containers

to this day because they're still radioactive dangerously. So the lack of understanding about the consequences of radiation exposure would have many more nasty consequences, just as it had with the X ray fad. For example, because radium is phosphorescent, it was seen as a useful material for stuff like

the hands of watches, like analog watches. He would paint an analog watches minute and our hands with radium, and that would make it glow in the dark and made it really easy to read the time, even if you were in low lighting. While the amount of radium on these watches was very very small and not likely to harm somebody who was wearing the watch, the employees responsible

for painting the watch hands received way more radiation exposure. Colloquially, they were called radium girls, and the management positions at these facilities frequently had significant protection from radiation, but the same could not be said for the women on the front lines, the women actually doing the work painting the radium onto these watch hands. It also wasn't uncommon for a worker to lick the end of her brush to shape it so that she could more easily paint the

watch hand. So that meant these workers were occasionally depositing little amounts of radium directly on their tongues. They were ingesting radium. Radium when ingested, will deposit itself in bone, much like calcium would, so several of the workers would ultimately grow ill with radiation sickness. A group of five of them later brought a lawsuit against their company. That

company was the United States Radium Company. They charged them with being irresponsible in areas of health and safety, and in turn that prompted a detailed study into what the long term effects of radium exposure are and it's awful that our knowledge came at such a steep price. At the same time, the results of that study would lead to massive changes in health and safety regulations for the

benefit of workers in the United States. From these discoveries, physicists began to learn more about the nature of radioactive material in general. They observed that there were different kinds of radiation beyond just calling it positive, negative, or electrically neutral. Some radiation seem to have more penetrative abilities. They could penetrate further into solid matter than other types of radiation.

So you might have one type of radiation that isn't able to penetrate solid matter effectively, and another one seems to go right through stuff as if there's no problem. A physicist named Ernest Rutherford conducted numerous experiments with radioactive material and at this point we were beginning to understand that radioactivity was a process in which certain materials undergo a process called decay, and that is the form that

they are in. The radioactive form is inherently unstable. You can if you want to think of it in terms of want, I mean putting motivation is ridiculous because we're talking about atomic particles here. But it's a form of an atom that does not want to be that form. It's unstable. So these materials will spontaneously but not necessary early, quickly break apart and give off energy and subatomic particles as they decay to a more stable form. Rutherford classified

three types of radiation. He said this was all based off the penetrative properties of radiation, how far they could penetrate into matter. The three types he classified were alpha radiation, beta radiation, and gamma radiation. Alpha particles had the least amount of ability to penetrate matter, and gamma rays were the opposite. They could very easily penetrate matter. Upon further study, scientists discovered that an alpha particle is relatively massive on

the atomic scale of things. It actually consists of an ejected helium nucleus. A helium nucleus is two protons and two neutrons. This is the type of radiation given off by a mera sirium to forty one. That's the radioactive material that's inside smoke detectors that I talked about in the last episode. The ionization chambers have this type of radioactive material in them, so you probably have some of

the stuff in your house right now. Alpha particles are not able to penetrate matter very well, and they're big enough and slow enough that they can't really get through skin, at least not most of the time, so they're not likely to have it affects you. Uh. They can't even go through very much air. After a couple of inches,

they've lost the energy to move forward. Breathing in alpha particles would be a real risk, and you wouldn't want to swallow any of it either, so you don't want to come into contact with the stuff, But having it enclosed in a smoke detector in its own little chamber in the smoke detector is more than enough protection that you wouldn't receive any sort of significant radiation exposure from

the ameer sirium inside a smoke detector. You would receive way more if you just went outside for a few hours. So it's not that big. It's it's it's like background levels of radiation UM. Beta particles are lighter than alpha particles, and they move fast. They're actually ejected electrons. They can travel further than alpha particles through the air. An alpha particle, like I said, I can only move a couple of inches,

but beta particles can move several feet. They're also moderately penetrating. They can pass through human skin, at least under the surface level of human skin, So if you're in contact with beta emitting material for a prolonged amount of time, you could suffer a skin injury like a skin burn. UH. Stuff that emits beta radiation includes carbon fourteen, sulfur thirty five, and strontium ninety UH. Those numbers at the ends of

those names are important that designates isotopes. Isotopes are forms of an atom that have a different number of neutrons, but of course they have the same number of protons and electrons. If you start having different number of protons, then you end up with a different element. So the most common form of carbon is carbon twelve. Carbon twelve has six proto ons and six neutrons, but you can also find carbon fourteen that has six protons and eight neutrons,

but it's unstable. It will undergo radioactive decay over time, so it will spontaneously decay and give off beta emissions. Gamma radiation, like X ray radiation, is a form of electromagnetic radiation. If you were to look at the full spectrum of electromagnetic radiation, radio waves are on one end with a very long, low frequency low energy waves. Gamma rays are on the opposite, so this is the very very very short wavelengths incredibly high frequencies. They pack a

ton of energy in them. X rays are slightly less energetic, but there are still far more powerful than visible light, which is why they can penetrate through solid objects better than visible light could, and gamma rays are even better at it than X rays are. These rays are electrically neutral, so magnetic fields won't cause them to change their paths. They'll just keep going straight. They can travel many feet through the air. They can penetrate several inches into human tissue.

In fact, it requires significant shielding to protect against gamma radiation. Radium two twenty six amidst gamma radiation, as do several other radioactive materials, And this is really dangerous stuff. It will not turn you into the Incredible Hulk, but it

might cause nasty, nasty problems for you. Now, in addition to all these observations and the growing realization that some forms of radioactivity posed a serious health hazard to humans, scientists discovered that these forms of radiation would interact with other particles and ionize them. That is, when the interaction would happen, the particles would have electrons split off of them, and by particles, I'm really talking about atoms and molecules,

I shouldn't use the word particle. I should say these atoms are molecules. When they would encounter this kind of radiation, they would have electrons stripped away, and the remaining molecule or atom would end up having a net positive charge because it just lost electrons. Electrons have a negative charge. Were referred to this general type of radiation as ionizing radiation.

It has created ions. Not all radiation is ionizing. Radio waves for example, are not ionizing radiation, nor are microwaves or visible light. These types of radiation don't have enough energy to ionize other particles, and it's why it's safe for us to broadcast radio waves and to walk around with radio waves going all over the place. They don't affect us, we don't interact with them. Makes sense that we would evolve in such a way where the radio

waves wouldn't affect us. This is why if you were to live next to a cell phone tower, you would not receive harmful radiation in the form of ionizing radiation,

because that's not the type that cell phone towers can emit. Uh, they just don't pack the punch at ionizing radiation like alpha, beta and gamma radiation as a different story, That stuff really can mess us up, and for that reason, it's a good thing to be able to detect it so that we can remove ourselves or the radioactive material from the environment that otherwise would pose a real threat to

our long term health. So when we come back, I'll talk more about what is actually going on with the radioactive interactions in our bodies, as well as the device used to detect it, and it's typically called a Geiger counter. But we'll be right back and I'll talk about then. Okay, So radiation interacting with the human body that ionizing radiation

can damage the cells in our body. Now, we have systems in our body that are really good at repairing damage, So it's entirely possible to encounter radiation suffer some damage as long as the damage. As long as the radiation wasn't so intense and the exposure so extreme that you didn't have uh, mortal wounds from acute exposure, you might

very well recover without any issue. But radiation can damage the d n A inside ourselves, and occasionally that can lead to other big problems, such as the development of cancer, which is why we say exposure to radiation increases your risk of developing cancer. It doesn't necessarily mean that we can easily draw a line from exposure to development, but we certainly know that it increases your risk of developing it.

It could be the reason that someone develops cancer. But there's so many variables it's impossible to say in any you know, given case, uh, specific cases, you might be able to trace it down, but now in general, you can't just easily make that that conclusion. It is clear that acute exposure to high levels of of ionizing radiation will cause injury and sickness and increase risk of more serious health problems further down the line. So we want to be able to detect that stuff early before we

risk having a longer exposure to it. Radiations invisible frequently exposure to lower levels of it could be very harmful, but they might not be noticeable. We might not register it just from our own personal experience. So how do we detect it? And that's where we get to the Geiger Counter. It's named after a guy named Hans Geiger Counter.

Now I'm just kidding, it's actually just Hans Geiger. Some people actually call these devices Geiger Mueller counters, because another guy named Valter Mueller took Geiger's design and tweaked it a bit about two decades after the initial invention of the Geiger counter to improve its performance. Some folks just

shorten this down to GM counters. But Hans Geiger was a physicist who worked very closely with Ernest Rutherford, whom I mentioned earlier as being the smarty pants who was classifying radiation as alpha, beta, and gamma, and Geiger came up with a device that initially was meant to detect alpha particles. He would eventually expand it so he could detect other types of radiation too, and he did it

with a pretty clever approach. Al Right, so I mentioned that these types of radiation have enough energy to ionize particles right to create electrically charged particles by stripping away electrons. So ions have a net electrical charge there. It's either positive or negative in general, but in this case we're talking about positive ions. And the movement of electrically charged particles has a name. It's electricity. That's what that is.

So thought Geiger. If I can create a device that detects the presence of ions, then it stands to reason that something in the area is causing these ions to form something like radioactive material over time. Geiger counters, like I said, would be able to detect all sorts of different types of radiation, but initially it was all about alpha radiation. And here's how it would work. A typical Geiger counter has a meter that's connected to a wand

or tube. So the meter is your indicator. The meter is what tells you if you get a hit, if there's a spike that indicates radiation. Inside the tube or the wand is a chamber, and inside the chamber is a low pressure gas and typically there's a a window made out of plastic on one side of this chamber. Also in that same chamber with the low pressure gas

is a thin metal wire of tungsten. You can almost think of it as like the filament on a light bulb, and the fire runs to the end of the tube that leads into the the cable that in turn attaches to the meter, and at the end of that wire there is an electrode with a high positive voltage. Now the other end of the wire is not connected to another contact. There's no complete circuit here, so you just

have a very high positive voltage on the wire. But it creates an electric field between the metal wire and the outside of the tube. So if the gas inside the tube, this low pressure gas, encounters ionizing radiation, then that radiation will strip electrons away from the gas molecules inside the chamber. The stripped electrons, because of their negative charge, will immediately zap the toungusten wire inside this one because again we've applied a strong positive voltage to that wire.

So the electrons having the negative charge are attracted to the positive charge of the tungsten wire. UH This usually means that there's a big rush of electrons. As electrons are moving, they will bash into other molecules, which will strip over other electrons, so you'll get a quick zap. Then you typically have to quench the Geiger counter, but that really doesn't matter for the rest of this discussion. I mean, it matters, but we're gonna focus on how

this is detecting things. So you get a bunch of electrons that hit this tungsten wire that creates a pulse of electricity, and the pulse is what feeds through a cable that goes to the meter, and the meter registers that there's been a pulse of electricity, which means that there's been the generation of ions inside this chamber, which in turn means you've encountered some sort of ionizing radiation. Uh. The wire might also pass the signal through an amplifier.

The amplifier will increase the power of that signal and send it to a loud speaker, and that's where you get that clicking noise. So if you've ever seen a movie where someone's using a Geiger counter and you're hearing a series of clicks, that's because the idea is that the wires picking up electric pulses due to ions, and then that's being sent to a loud speakers, so that's what's making the clicking noise. The beauty of this design is that it isolates the ions source from the environment.

Right the source of the ions is this gas inside a chamber. The gas is kept separate from the surrounding environment, so you don't have to worry about somehow encountering ions out in the wild, Like if you were standing next to an ion generator. Let's say you've gotten ionization purifier, something that's meant to purify the air in your room, you shouldn't get a readoubt from your Geiger counter because the ions being generated by this ionization chamber would not

be interacting with the gas inside the Geiger counters chamber. Instead, the only time the gas and the Giger counter should be ionizing at all is if you're coming into range of ionizing radiation. So dependent upon the intensity of the readelts you're getting, you would know kind of how much

radiation you were experiencing at any given moment. And again, radiation exposure on its own does not immediately mean that you mutate or you you know, suffer terrible injuries unless it's an incredibly intense amount of radiation uh at very high energies. But it does mean that you need to, you know, get out of there and to find some

other place to be. One thing I didn't really talk about in this episode was the concept of half life's and that is important because half life's also give us an idea of how long radioactive material could potentially remain dangerous.

And when you're looking at half lives that are on thousands of years, you're talking about uh, time that extends beyond that which humans have been on Earth right as at least as human beings as we understand them, but we might trace it back to an earlier evolutionary form of humans. But you start looking at some of these materials and you realize, wow, this stuff is going to be radioactive for longer than humans have been walking around

on Earth as human beings. Uh. That's why you get people who are concerned about things like nuclear power, where one of the byproducts of nuclear power tends to be nuclear waste that is radioactive. Some of that nuclear waste will be radioactive and dangerously so for a relatively short time.

But there are other types of nuclear waste that will be radioactive for a very long time and sure in uh it's not emitting radiation at a level high enough for it to you know, be dangerous if we don't treat it carefully, but it's persistent and and long time exposure to it will increase our risk of developing really nasty diseases like cancer, So that's where that concern comes in. Now.

There are a lot of different approaches to nuclear power to mitigate the creation of nuclear waste, and there are a lot of plans on what to do with that nuclear waste to try and keep it far enough away from people to not be a problem, but that all runs into a lot of other social issues that are

harder to solve than technical issues. Um. On the flip side, we're also looking at possibilities like fusion power, which is very different from the fission process that generates a lot of nuclear waste, but those are topics for a different episode. I hope you have a greater understanding of how radiation works and what it actually means, as well as how

Geiger counters work. Again, I think it's a very elegant way to try and detect radiation it's not so much detecting the radiation directly, but rather the effects of radiation on something that we can more easily observe directly. And I think that's a very clever approach to uh to creating a meter. If you guys have suggestions for future episodes of tech Stuff, reach out to me and let me know. On social media, the handle at both Twitter

and Facebook is exactly the same. That handle is text stuff H s W and I'll talk to you again really soon. Text Stuff is a production of I Heart Radio's How Stuff Works. For more podcasts from I heart Radio, visit the I heart Radio app, Apple Podcasts, or wherever you listen to your favorite shows.