Hello.
My name is Bruce Doran.
I'm one of the scientists
that works here
at Science North.
And in this video,
we are going to look at
the concepts of light,
optics, radiation,
and specifically ionizing
and non-ionizing radiation.
So, you might hear
the word "radiation"
oh no,
and you might think of
nuclear waste products
and things like that,
but radiation
is a general term that we give
for any forms of energy
that are within
what we call
the electromagnetic spectrum.
And there's many, many different
forms of energy
within that spectrum
going from radio waves,
microwaves, infrared,
visible light
is part of that spectrum,
ultraviolet, x-rays,
all the way to gamma rays.
All right?
So there's many, many different
forms of radiation and energy.
Now, what's really interesting
is that
some forms
of this radiation
will have more energy
than others.
So what we're going
to do is
we're going to do
a very quick experiment.
So, I have some fluorescent
paper right here.
And what's neat
with this fluorescent paper is
depending on the amount
of energy you put in--
if you put in lots of energy
or energy with high--
or light with
high levels of energy,
it will then fluoresce
and give back light.
So, let's try two different
forms of light.
So I have a, you know,
laser here with green light
and we're going to see
what happens
with the green light here.
All right?
So we see
no fluorescence.
So it's probably
very low energy.
Now let's try with this light,
more on a UV range.
And if we see,
look at that!
That's actually fluorescing.
So what this tells us is
that UV light has more energy
than green light.
So, what does that mean?
How is that related to ionizing
and non-ionizing radiation?
Ionizing radiation comes
or is radiation that has
high levels in energy.
Essentially what ionizing
radiation will do is
it will knock off
an electron,
it has so much energy,
it will knock off an electron
from an atom or a molecule
causing it
to become an ion.
Non-ionizing radiation
doesn't have that much energy,
cannot knock off
an electron,
and therefore does not create
different ions, okay?
How come we have
different levels of energy?
Well, it all depends
on the wavelengths.
If you have wavelengths
that are very long
like radio waves
or microwaves,
very low energy level,
non-ionizing radiation.
When you have wavelengths
that are very short,
it means they have
high levels of energy,
so we are dealing with
ionizing radiation, okay?
So that's how we can tell
the difference between the two.
And when you actually
look at this,
from ultraviolet to x-rays
to gamma rays,
you are increasing
your amount of energy
that's there.
Now, that's not to say,
you know,
these kinds of radiation,
we should take them lightly.
For example,
gamma rays,
a lot of people think,
you know,
you've got a dose
of gamma rays
and the next thing
you know,
you're kind of green
and very, very angry.
Well, that's not
how it works.
Gamma rays
have so much energy,
it can actually destroy DNA
in your cells.
You can actually get
radiation sickness,
and you can have
some severe burns, all right?
So it's not what we see
in the comics.
So, what I want to do
right now is
show you a piece of
instrumentation
that we have here
at Science North
which will help us
visually see
the different forms
of radiation,
and specifically,
ionizing radiation,
high level particles
or energy
that actually bombard
our planet.
Come with me and I'll show you
that piece of instrument.
So this piece of instrumentation
is called a cloud chamber.
It is made up of super saturated
alcohol in a vapour form.
Now, what's really neat
with this instrument,
it can actually detect
ionizing radiation.
So when high energy particles
hit this cloud chamber,
what happens, it will ionize
some of the vapour molecules
and by ionizing them,
what happens, the vapour
molecules will have a charge
and then
the other vapour molecules
will be attracted
to it
and the end result of this,
you actually see a cloud
or a streak.
So what you see right now
is a whole bunch of streaks
coming from high-energy
particles or ionizing radiation
and where these different forms
of radiation are coming from?
Well, it's actually
coming from space
and also from the sun.
So I will do
a quick demonstration.
I have a piece of radioactive
material, gamma ray,
and by putting it on there,
we are going to see a change
in what we're seeing here
in the of number streaks
that we can see.
So what that is actually
telling us is that
we actually have
different forms of radiation
ionizing radiation
emitting from that,
hitting the cloud vapour
and what we're actually seeing
right now
is a whole bunch
of streaks
caused by
this ionizing radiation.
So ionizing radiation
and non-ionizing radiation
is found all around us
and is just part of life.
So let's look at ray diagrams
a little bit more closely.
And we're going to use
two examples of telescopes
to really see ray diagrams
a bit up close.
This type of telescope
is actually called
a Newtonian telescope.
And what's really neat is that
the light comes in,
hits a parabolic mirror.
It comes back,
hits a flat mirror
that then goes up
an eyepiece.
So if we see, I have a light
hitting right there,
it goes into the telescope
and then comes out
right here.
This type of telescope
is very, very different.
It's a Galilean telescope.
Essentially,
it doesn't use mirrors
but, in fact,
uses lenses.
So light comes in.
So, I've got some light
coming in here,
goes through
a set of lenses,
convex lenses,
and then through
another set of lenses
and then
comes out here.
Now, the trouble
about using lenses is
as light goes through lenses,
it's a bit like a prism,
it will actually cause
parts of the light spectrum
to kind of diffract
and kind of segment,
so what you need to do is
you need a double lens
right here
to deal with what is called
chromatic aberration.
If you don't have that,
then your image
doesn't look good,
it gets
kind of fluid,
and then another set of lens
right here to deal with that.
So it's called a doublet
or a doublet set of lens
to deal with
chromatic aberration.
So what we're going
to do now is that
we're going to see how
the different light rays
actually go through
the telescope
using a special type of machine,
a fog machine.
So I'm going to go grab
the fog machine
and I'm going to show you
right now.
All right,
so here's my fog machine.
So let's see what happens
when I put it on the telescopes.
Pretty cool.
So what we're seeing is
a very simplified ray tracing
of both telescope.
When you actually do
ray tracing,
what you usually do is
you take
all the different wavelengths
of light or different light
as it comes down
into the different telescopes
in order
to give an image.
The reason why
we're only seeing
one ray or one line
in this case
is because
we're using lasers
and lasers will concentrate
all the wavelengths of light
into one single point,
and that's why we are seeing
this one single line right now.
So it's not something
that's, like, abstract.
It's real.
And you can actually use ray
tracing to see how light
bounces off surfaces
and where it ends up.
