What is a “Coulomb” or a “Roentgen”?
Coulomb or Roentgen is the measure of
transfer of energy & resulting ionization.
Who discovered X-Rays and when did this happen?
William Roentgen discovered X-Rays in 1895.
Who discovered Gamma Rays and when?
Marie and Pierre Curie discovered Gamma Rays in the late-1800s.
What do X-Rays and Gamma Rays have in common?
They are both forms of electromagnetic wave radiation
with enough energy to ionize.
What do Radio, TV, Radar, Infra-Red, Visible Light, Ultra-Violet and Micro electromagnetic energy waves have in common?
They do not have enough energy to ionize atoms they encounter.
(They don’t have the energy to remove electrons from those atoms.)
What is the Atomic Number (Z) referring to?
Atomic Number (Z) = the number of protons in the nucleus of an atom.
What is the Mass Number (A) referring to?
Mass Number (A) = total of protons & neutrons in the nucleus of an atom.
N = (A) - (Z)
eg. Uranium 238 has a mass number (A) of 238 and an atomic number (Z) of 92, therefore the number of neutrons will be: 146
What is Coulomb’s Law?
Coulomb’s Law states that this is the binding energy or attraction force which is greater the closer the electrons in orbit are to the nucleus.
This same binding energy decreases as the electron shells move away from the nucleus.
What can X-Ray radiation produce with its ionizing effects?
- can cause certain material to fluoresce
- can produce chemical effects
- can cause biological effects (eg. deterioration of living cells)
- gasses bombarded by radiation can become electrical conductors (eg. ionization detectors)
X-Rays and Gamma Ray radiation share properties that are important to know. What are they?
- they travel in straight lines
- they are not affected by electrical or magnetic fields
- they cannot be focussed
- they affect photographic chemical emulsions
- they damage or destroy living cells, produce burns and can produce changes to blood or blood-forming organs
- they cannot be detected by human senses
What are some characteristics of an Alpha (⍺) radiation particle?
- they are large & slow moving
- they quickly give up their energy
- they cause ionizations along a short path
- they cannot penetrate a layer of dead skin
- they are most hazardous when they are ingested or inhaled
What are some characteristics of a Beta (β) radiation particle?
- they are very light and fast moving
- they have an electrical charge of -1
- they are easily deflected & scatter as they pass through matter
- they can be absorbed by a few mm of aluminum
- they can travel a few hundred cm before losing energy
What are some characteristics of Neutron (n) radiation particles?
- they are not normally emitted during the natural decay process
- they have the same mass as a proton
- they no electrical charge
- spontaneous emission can occur without the interaction of a photon
- they are best shielded against by water
What is RAD or Radiation Absorbed Dose?
How is it now measured?
RAD is the quantity for
RAdiation Damage in living tissue.
It is now measured in Grays (Gy)
which is defined as 1 Joule of energy absorbed
per kg of tissue mass.
1 RAD = 10 mGy
1 GRAY = 100 RADs
What is another name for REM?
Dose Equivalent
What is the SI unit used for Dose Equivalent (aka REM)?
Sievert (Sv)
What is a Sievert?
The dose from ANY radiation source that produces biological effects.
How is the Dose Equivalent (aka REM) determined?
Multiply the absorbed dose (dose rate x time exposed)
by the Q Factor (Quality Factor).
Sv x Q = Dose Equivalent
(in SI units)
OR the old way…
RAD x Q = REM
What formula is used to find the remaining activity of an isotope
or
the number of half-lives used?
A1 = Original Activity
A2 = Unknown Activity
n = Number of Half-Lives
What is the Photoelectric Effect?
Hint: When photons strike, similar to the Compton Effect.
- Gamma ray collides with an atom’s orbiting electron,
- electron absorbs ray’s energy, ejects the electron from orbit
- a free electron is created
- a (+) atom is created
When does Pair Production occur?
At 1.02 MeV or greater.
What is the Compton Effect?
Hint: When photons strike, similar to the Photoelectric Effect.
- Gamma ray collides with an atom’s orbiting electron,
- electron doesn’t absorb energy but gets knocked out of orbit
- continues along with remaining gamma wave to collide with other electrons
- a free electron is created
- a (+) atom is created
What happens when Pair Production occurs?
- gamma ray photon disappears
- a positron and an electron are ejected from the atom
What happens in the case of Coherent Scatter?
- gamma ray photon goes through an atom without hitting anything
- low energy is released by the resulting vibrating electrons
