Radiation P1 Flashcards
What is an alpha particle?
A helium nucleus emitted by radioactive substances
Describe the structure of an alpha particle
Consists of two protons and two neutrons, relative mass is 4 and charge is +2
What can alpha particles be stopped by?
Paper
What is a beta particle?
A fast moving electron emitted by radioactive decay
Describe the structure of a beta particle
Consists of an electron emitted when a neutron in the nucleus turns into a proton, relative mass is 0 and charge is -1
What material stops beta radiation?
Aluminium
What is gamma radiation?
A high energy, high frequency wave
What is gamma’s charge and mass?
No mass or charge
What can gamma radiation be stopped by?
Lead
What happens when an element emits an alpha particle?
It loses two neutrons and two protons so the atomic mass decreases by 4 and the atomic number decreases by 2
What happens when an element emits a beta particle?
The atomic mass is unchanged but the atomic number increases by 1 because a neutron turns into an electron and proton
What happens to an element when it emits gamma radiation?
Does not alter mass or proton number
Define ionising power
How easily different types of radiations can cause other atoms to lose electrons and form ions
Which type of radiation is the most ionising and why?
Alpha because it has the highest charge so highly ionises atoms easily as it passes them
Which is the least ionising and why?
Gamma as it is a wave without charge which does not interact with atoms when it touches them
Why would an older source of cobalt be less radioactive than a new one?
It’s had time to decay
Why can’t we predict when a particular atom will decay?
It is a random process however we know a fixed amount will decay each time
What is the half life of an isotope?
The average time it will take for half of the nuclei present to decay. If the half life of a sample was 30 years, half of its nucleus would decay in the first 30 years then in the next 30 years a quarter of the original sample would decay (half of the new amount (half of one half)) then after another 30 years one eighth of the original sample would decay (half of the new amount (half of quarter))
Why can gamma radiation penetrate further?
It has no charge or mass but this means they are weakly ionising as they tend to pass through rather than collide with atoms
Why is radiation dangerous?
Can enter living cells which can mutate incorrectly and become cancerous or they can be killed off completely
Name 2 natural sources of background radiation
Radon, cosmic rays
Name 2 artificial sources of background radiation
X rays, nuclear power
Define ionising radiation
Different types of radiations cause other atoms to lose electrons and form ions
What is a use of alpha particles in the home?
Used in smoke detectors by ionising air particles causing a current to flow. If there is smoke in the air is binds to the ions meaning the current stops and the alarm sounds
What is a use of beta radiation?
Beta emitters are used to test the thickness of sheets of metal because they are moderately ionising so the particles are not immediately absorbed by the material like alpha radiation would be and do not penetrate as far as gamma rays. Therefore slight variations in thickness affect the amount of radiation passing through the sheet
How can radiation be measured?
With a Geiger-Muller tube and counter which records the count rate (number of radiation counts reaching it per second)
What can half life be used for?
To find the rate at which a source decays -its ACTIVITY which is measured in becquerels, Bq where 1Bq is 1 decay per second
What is the problem with trying to measure how long it takes for nearly all unstable nuclei to decay?
Activity never reaches zero
What does it mean to irradiate something?
Be exposed to a radioactive source
Identify 3 ways of reducing irradiation
Keeping sources in lead lined boxes, standing behind barriers or being in a different room and using remote controlled arms when working with radioactive sources
Define contamination
Unwanted radioactive atoms getting onto or into an object , these contaminating atoms may then decay to release radiation which would cause you harm as radioactive particles could get inside your body
How can you avoid radioactive particles getting stuck to your skin and under your nails or getting breathed in?
Use gloves and tongs when handling them, wear protective suits to stop you breathing the particles in
Why is irradiation from beta and gamma sources more dangerous than from alpha?
Outside the body beta and gamma can penetrate the body and get to delicate organs whereas alpha is easily blocked by small air gaps and cannot penetrate the skin
Why is contamination from alpha the most dangerous?
Inside the body alpha do all their damage in a very localised area whereas with beta sources radiation is absorbed over a wider area and some passes out of the body altogether and gamma mostly pass out straight away
