Radioactivity Flashcards
(39 cards)
What is the stability of atoms
Protons are held in the nucleus by the nuclear force that is strong enough to hold the nucleus together against the electric force repelling the protons away from each other , too many or too few neutrons affect this balance between forces and create an unstable nucleus that will idecay and give out energy and alpha or beta particles
What is ionising radiation
Causes atoms to gain or loose electric charge , given out by unstable nucleus at random
What is alpha radiation
Fast radiation thrown out of untabale nuclei , alpha particles , helium nuclei (2 protons and 2 neutrons ) , have a charge of +2. They have. A short range and can travel a few centimetres and can’t penetrate more than a few mm of paper . This is because they interact with atoms along their path , forming ions so they rapidly give up energy , they are very big as well which means high ionising ability
What is beta beta particles
Fast moving electrons ejected from decaying nucleus , beta decay involves a Neutron splitting into proton and electron . Atomic number increases by 1. Electron is ejected whereas proton stays inside . Mass number stays the same . Very light and have a charge of -1. Interact with matter in the paths less frequently than alpha due to smaller and less charge so they have a lowervionising ability but greater range and can travel long distances through air and are stopped by a mm of aluminium foil
What is gamma rays
Electromagnetic waves with short wave length . No mass , no charge . Weakly ionising and Interact occasionally with atoms in their paths . Very penetrating and pass through all but the very densest of materials . Takes thick lead or a metre of concrete to stop gamma, emitted in packets of energy called photons
What is bq
Measure of how many unstable nuclei are disintegrating per second
How do scientists use photographic film
To secrecy radioactivity , those who work with radioactive materials were a strip of photographic film on a badge and if the film Is fogged then the scientist has been exposed to too much radioactivity
How does Geiger miller tibe work
Ions are detected by electronic circuit and it’s linked to a counting circuit which counts the number of ionising particles
What Is background radiation
Low level ionising radiation produced all the time from ground and buildings , nuclear power , cosmic rays , food and drink . Decay products from when the earth was formed .
WhT is radioactive decay
Exponential decay , the smaller the quantity the more slowly the quantity decreases, rate of decay falls as time passes because there are fewer nuclei to decay
What is half life
The average time taken for half the original mass of the radioactive sample to decay . Half life is different for different radioactive isotopes .
How do we measure half life
Use a Geiger miller tube
First measure background radiation which must be subtracted to know the radiation produced by the sample itself , then rate of decay is measured at regular time intervals
When do we need isotopes with short half life’s
Medical and radioactive tracers so they don’t remain in the patient or water supply for a long time
When do we need long half life
Carbon dating as the activity would be too difficult to measure accurately if it stops below a certain level
How are radioactive tracers used in medicine
Taken orally by patient and its passage around the body can be traced with a gamma camera , short half life important so the tracer has very low activity in a few days
Radiation therapy
High dose of radiation cause the normal function of cells to changes which can lead to abnormal growth and cancer very high doses kill cells , this can alone used to sterilise EQuiptmnet as they can be packaged and the radiation will then penetrate the package and destroy bacteria without damaging the item
How do gamma ray cameras work
Source of gamma placed on one side of an object and gamma camera on the other , more penetrating than X-ray and sources are smaller and does not require power source or large equiptmnet like X-rays
What is gauging
Uses to measure how much material there is in a storage vessel . Coal absorbs the radiation so it lowers the detector count , monitoring amount of radiation can show how thick a sheet is for it to be controlled in manufacturing
Tracers in pipes
Uses for leaks to track the flow of liquid , radiation can be detected so there will be more radiation in a leaky area
What is radiocarbon dating
Used to find the age of organic matter , measure the level
Of carbon 14 from carbon dioxide when an animal dies the carbon is no longer replaced by breathing and the carbon decays and the proportion of radioactive to stable carbon decreases . The half life is 5600 years. The Age can be estimated by comparing the amount of carbon 14 in the dead matter to the living organism .
What are limitations of carbon dating
Assumes cosmic radiation on earth is constant and can’t be used to date samples over 60,000 years as after 10 half live the amount of carbon is too small to measure accurately
How are rocks dated
Don’t absorb carbon 14 so a different method is used . Proportion of parent to stable daughter nuclide measures to give an age of the rock
When is alpha risky
If taken into body as highly ionising but has little penetrating power . Radiation can cause cells to mutate due to damage .
When is beta and gamma risky
Outside the body as they can penetrate skin and flesh. The longer period of exposure the greater the risk
