Medical Physics Flashcards
What is an atom
The smallest single piece of an element
What are the three sub-atomic particles within an atom
+ protons
+ neutrons
+ electrons
What is an ion
An atom that has gained or lost electrons meaning it has become positively or negatively charged
What is an element
A substance which contains only one type of atom
What is an isotope
An element which has the same atomic number as another element, but a different mass number (different number of neutrons in the nucleus)
What is an unstable nucleus
One which has either too many or too few neutrons in its nucleus
What is the way to determine an atoms stability
Proton:neutron ratio
How do nuclei become stable
By emitting radiation, a process known as radioactive decay
What are the three types of radiation
+ alpha
+ beta
+ gamma
What is alpha radiation
A helium nucleus consisting of two protons and two neutrons
What is beta radiation
Fast moving electrons
What is gamma radiation
High frequency EM waves
What is the charge of:
A: alpha radiation
B: beta radiation
C: gamma radiation
A: 2+
B: 1-
C: negligible
What is the range in air of:
A: alpha radiation
B: beta radiation
C: gamma radiation
A: 5 cm
B: 10 m
C: almost infinite
What is… absorbed by:
A: alpha radiation
B: beta radiation
C: gamma radiation
A: a sheet of paper
B: 3-5 mm of lead
C: thick concrete
What are three ways to prevent exposure to radiation
1: limit the time expose to the radioactive source
2: shield yourself from the source
3: keep at a relatively far distance from the source
What is ionisation
The gain or loss of electrons from a stable atom
How does alpha radiation cause ionisation
The positively charged alpha particles attract the negative electrons away from their atoms
How does beta radiation cause ionisation
The negatively charged beta particles repel the negative electrons, causing them to shoot away from their atoms
How does gamma radiation cause ionisation
The gamma particles collide with the atoms with large amounts of energy, knocking the outer electrons away
What are three ways of detecting radiation
+ a Geiger muller tube
+ a spark counter
+ a film badge which changes colour depending on the amount of radiation absorbed
What is background radiation
The naturally occurring radiation already found on earth
What are two examples of background radiation
- food and drink
- gamma rays from granite
What is the activity of a radioactive source
The number of nuclei that decay per second
