2. What is Radiation
• What is radiation?
• Do you have detectors in our homes?
• Do you have radiation sources in your homes?
• Radiation is energy that radiates from a
source…
• i.e. Light, Heat, X-Rays, etc.
• As we can see there are many different
types of radiation
3. What is Radiation
• Why is there radiation?
• In nature there are “stable” and “unstable”
nuclei
• Neutrons are the “binding force” of an atom
• The greater number of protons, the more
and more neutrons are required to hold the
atom together… #’s neutrons in stable
atoms is not always the same # of protons
4. What is Radiation
• Since like charges repel one another, the
more protons you have repelling each other
in different directions….many more
neutrons than protons will be required
• As an atom approaches stability the changes
in the nuclei cause radiation, the stability is
gained by the ratio of neutrons and protons
coming closer to 1/1
5. What is Radiation
• The physical characteristics of radiations
include; mass, charge, point of origin
(where it’s found)
• There are two possible points of origin
• Nucleus
• Electron Cloud
• Most radiations originating outside the
nucleus are not in the scope of this course,
these including…visible light, radio, etc.
6. What is Radiation
• Radiations also can be characterized by
their effects on matter
• When atoms are exposed to radiation they
are either created into ions or not, therefore
we classify radiation as either…
• Ionizing
• Non-Ionizing
• In this course we are concerned only with
ionizing forms of radioactivity
7. What is Radiation
• There are two major types of ionizing
radiation
• Particulate Radiation
• Electromagnetic Radiation
• Particulate Radiation is solid matter,
consists of particles, therefore has mass or
substance
• Electromagnetic Radiation is made up of
waves of pure energy, therefore having no
mass
8. What is Radiation
• There are three types of particulate radiation
• Alpha
• Beta
• Neutron
• Alpha radiation is made of 2 protons and 2
neutrons, therefore having an atomic mass
of 4 (ionized helium nucleus)
• Alpha radiation has a charge of +2 and as it
travels through air it “ionizes” atoms
9. What is Radiation
• Alpha particles are emitted from the nuclei
of large atoms ~ 80 protons and up
• The reason large atoms give off “large”
particles i.e. alpha particles is because they
are very unstable therefore need to give off
large amounts of mass
10. What is Radiation
• Beta – Beta particles are made up of
electrons
• They have a mass of 1/2000th AMU and can
have either a + or – charge
• Even though positive electrons are not
supposed to exist, under some
circumstances they can be produced in the
nuclei of atoms
• These positive electrons (positrons) are
more commonly known as antimatter
11. What is Radiation
• Beta particles are a result of protons and
neutrons changing identity
• When a neutron changes to a proton
(neutron conversion) a negative electron is
emitted
• When a proton changes to a neutron
(positron emission) a positive electron is
emitted
• Discuss electron capture
12. What is Radiation
• When the negative electron leaves the
nucleus, it travels close to the speed of light
• This is mainly due to its extremely low
mass
• However, when the positron leaves the
nucleus, being antimatter (+), it
immediately runs into a negative electron
and there occurs a matter/antimatter
annihilation…Example, Na22 gives off a
positron and can be measured at 511 KeV
20. What is Radiation
• Neutrons are the last type of particulate
radiation that we will discuss
• Neutrons have a mass of 1 AMU and ø
charge
• They are produced most commonly in
nuclear reactors from when atoms fission
21. What is Radiation
• Now that we have looked at the types of
particulate radiation, we will now look at
the types of electromagnetic radiation
• Remember electromagnetic radiation is
waves of pure energy for example; light, x-
rays and all other members of the
electromagnetic spectrum
22. What is Radiation
• Gamma – Gamma rays are electromagnetic
rays of pure energy
• They have no mass and no charge
• Gamma rays are produced as a result of the
de-excitation of the nucleus of atoms that
have given off either an alpha or a beta
particle
• Gamma rays are measured in KeV =
Kiloelectron Volts
23. What is Radiation
• X-rays have the same general
characteristics as gamma rays… the only
difference is where they are emitted from
• We will discuss x-rays later in the course
when we look at medical applications of
radiation
24. What is Radiation
• Gamma rays are measured in KeV =
Kiloelectron Volts
• Particulate Radiation is measured in MeV =
Million Electron Volts
25. What is Radiation
• When we looked at the atom we learned the
term “isotope” we have also seen the
difference between stable and unstable
atoms… it is important to know that an
element can have both stable and unstable
isotopes
• Unstable isotopes are all radioactive
26. What is Radiation
• The term Nuclide refers to any atom where
the mass is stated and the atomic number is
either stated or inferred, i.e. U238, 92U238
• This is where the chart of the Nuclides
comes from, this chart shows all elements
AND all the known isotopes of those
elements
• We will look at this chart in detail later in
the semester
Editor's Notes
Discuss electromagnetic radiation
It’s like having a valley with very steep sides…. The rocks on the hillside want to roll down… even though it may stop, it still wants to be at the bottom.
We know this because we can see the results in a lab that we are going to do later in the semester keV = Kiloeclectron Volts
You can have an alpha or beta without a gamma, however, you can’t have gamma without alpha or beta.
You can have an alpha or beta without a gamma, however, you can’t have gamma without alpha or beta.
You can have an alpha or beta without a gamma, however, you can’t have gamma without alpha or beta.
