Radiation can be a scary word for a lot of people.
But just what is radiation exactly?
I mean, you probably know that it’s responsible for such 1950s monster movies like Godzilla,
but that doesn’t tell us much.
Radiation in the sense that we normally mean the word was discovered in 1896 by Henri Becquerel
when he discovered that uranium could fog a piece of film.
But even that definition of radiation is incomplete.
So what is radiation, exactly?
Radiation is the emission of energy by a substance.
There are lots of kinds of radiation.
There is electromagnetic radiation and nuclear radiation.
Electromagnetic radiation encompasses such things as radio waves, microwaves, infrared,
visible light, ultraviolet light, x-rays and gamma rays.
These are all pretty familiar and aren’t what we normally mean when we talk about radiation.
I mean, microwaves can cook things and ultraviolet light can give you a sunburn, so it’s not
like electromagnetic radiation can’t be dangerous, but it’s generally not what people
mean when they talk about radiation.
Actually, gamma radiation is an example of that kind of radiation, but we’ll return
to that in a bit.
When people talk about radiation, they mostly mean nuclear radiation, which is when subatomic
particles are emitted from the nucleus of atoms.
I should also say that nuclear radiation is sometimes called ionizing radiation, as it’s
energetic enough to knock electrons off atoms.
But I’ll call it nuclear radiation to remind you of the radiation’s origin.
And there isn’t just one kind of nuclear radiation.
There are at least four different kinds.
There is alpha radiation, beta radiation, gamma radiation and neutron radiation.
Each of these types of radiation have different characteristics.
Alpha radiation is when an atomic nucleus shoots out an alpha particle, which consists
of two protons and two neutrons.
If you dust off your chemical knowledge, you’ll recall that the nucleus of a helium atom contains
two protons and neutrons, so alpha radiation is when a radioactive element shoots out a
helium atom, minus the electrons.
Beta radiation is caused when an atomic nucleus shoots out an electron.
We could call it electron radiation, but the name was invented before we identified the
emitted particle as an electron.
It generally occurs when a neutron in an atomic nucleus turns into a proton and electron.
The proton is kept inside the nucleus and the electron escapes.
Gamma radiation is when an extremely high energy photon escapes the nucleus.
In a sense, this isn’t different much different than a nucleus emitting ordinary light, but
the much higher energy involved means that the gamma ray can damage surrounding material.
Gamma rays are often used in comic books to give super powers to unsuspecting spectators.
By the way, x-rays are similar to gamma radiation in many ways, but less energetic.
They are like gamma radiation’s younger and less successful sibling.
And then there is neutron radiation, which is just the emission of a neutron.
In a sense, this is the most dangerous type of radiation but, as we will see, that’s
a subjective statement.
So, these are the different kinds of radiation that one encounters in nuclear physics.
But, as we will see, they have radically different properties.
This isn’t a radiation safety video, but it’s important to know at least broadly
what you need to do to be safe around radiation.
Perhaps obviously, the easiest thing to do is to just get far away from radiation.
Just like a fire seems cooler, the further you get from it, distance is the easiest way
to reduce your exposure to radiation.
However, that’s not always possible.
We live in a radioactive world.
Bananas are radioactive, as are Brazil nuts.
Heck, you are radioactive.
I made another video discussing levels of radioactivity and, if you watched that, you’ll
understand that low levels of radioactivity are not inherently dangerous.
But there are things you might encounter that are more dangerous- things like dental x-rays
for example.
Now don’t worry about dental x-rays- they give you a very low dose and are definitely
worth having, but if you’re for example, a dental hygienist, you might encounter lots
of x-rays and want to protect yourself.
So it’s important to know about the ways in which you can shield yourself from various
kinds of radiation.
Alpha radiation consists of heavy and slowly moving particles with a lot of electrical
charge.
These properties combine to make them easy to stop.
You can stop alpha particles using a single sheet of paper.
Here- I’ll show you.
Here is a sample that emits alpha particles and a Geiger counter.
The paper stops the radiation.
Beta radiation consists of light and fast moving particles with electric charge.
This means that they can be stopped by reasonably thin plates of material.
For instance, we see here that they can be stopped by a thin metal plate.
Gamma radiation consists of fast moving particles with no electric charge.
This means they emit no electric fields to interact with matter.
They are therefore much harder to stop.
To stop gamma rays, you need a heftier chunk of dense material like lead.
This is also true for x-rays, which is why they put a lead apron on you when you’re
getting dental x-rays.
Neutron radiation consists of pretty heavy particles with no electric charge.
Since they don’t interact with atomic electrons, they can travel long distances- say hundreds
or even thousands of meters in air.
The way to slow them down is not so intuitive.
You have to use something with a lot of hydrogen in it, like water or plastic.
The neutrons hit the protons in the hydrogen nuclei and knock them out.
This stops the neutrons and then the charged protons are stopped quickly much like alpha
particles are.
By the way, given the clicking noises you heard, you might be wondering if the technician
doing the demos here was in any danger.
The answer is no.
The radioactive sources we used were real, but they were weak.
This diagram shows you roughly how to shield the various kinds of radiation.
It summarizes what I’ve just said.
So I’ve told you about how to protect yourself from radiation- distance and shielding.
And, for shielding, I’ve told you what works for what kinds of radiation.
But what if you can’t move away or get shielding?
What impact to these types of radiation have on human tissues?
This is kind of interesting.
It turns out that the different types of radiation have distinctly different consequences in
terms of biological damage.
In order to figure this out, scientists took different kinds of radiation and aimed them
at various kinds of tissue and saw how much biological damage occurred.
They then came up with a number that would account for the differing amounts of damage
observed.
This number is called a quality factor, or just Q.
If Q is one, that means there is no adjustment.
If Q is greater than one, that means that this particular kind of radiation is biologically
more dangerous than other types of radiation.
So, we see here a chart that shows the Q factor for different kinds of radiation.
We see that gamma and beta radiation and x-rays have a Q factor of 1, which means that they
don’t have an enhanced damage capability.
But slow neutrons have a Q of 5, which means that for the same amount of absorbed radiation,
more biological damage occurs.
Fast neutrons have a Q of 10 and alpha particles have a Q of 20, which means that they do more
biological damage than other kinds of radiation.
That last one is kind of weird.
I mean, alpha particles are easy to stop, but do more damage in living tissues.
But, if you think about it, this makes sense.
When an alpha particle stops, it stops hard, and deposits all of its energy in one place.
This means when it hits a cell, the local damage is extensive.
This is especially true if you are unlucky enough to inhale alpha emitting radioactive
dust.
That’s extremely dangerous.
So I hope that this video this kind of gives you an idea of the diversity of possible kinds
of radiation.
I mean, there isn’t a single kind and that means that if you want to understand radiation
and how to react in a certain situation, you really do need to become informed.
However, that does take work because, in the end, understanding radiation is like your
Facebook status when you’re deciding if you want to get back together with your ex.
It’s complicated.