Topic 6 - Using radioactive materials Flashcards
What is background radiation
low-level radiation thats around all the time
Where does background radiation come from
naturally occurring unstable isotopes found in air, food, boiling materials, rocks etc
Space
Why does the level of background radiation depend on where you live
certain underground rocks (e.g granite) can cause higher levels of background radiation at surface especially if they release radioactive radon gas.
What is half life
time taken for half the un-decayed nuclei to decay
What is radioactive activity measure in
becquerels (Bq)
how do you calculate half life
step by step, keep halving until you get the answer
What is a use of alpha radiation
fire alarms
weak source of alpha radiation is placed in a smoke detector close to two electrodes.
source causes ionisation which allows a current to flow
smoke absorbs radiation so current stops and alarm sounds
How are gamma rays used to sterilise food and equipment
food can be irradiated with high dose of gamma rays which will kill all microbes so food won’t go bad as quick. Medically equipment treated the same.
need a strong emitter of gamma rays with reasonably long half life so doesn’t need replacing that often
Why is irradiation better than boiling for sterilising
doesn’t involve high temperatures so fresh fruit or plastic instruments won’t be damaged.
how are gamma and beta used as tracers
injected or swallowed into patient and progress through the body is followed by detector. Computer uses reading from detector to produce an image. can be used to diagnose medical conditions e.g cancer
why must tracers be beta or gamma
so it passes out of the body
should have short half life
How is gamma used to detect leaks in pipes
place tracer in pipe, where largest amount detected the leak is
how is beta radiation used in thickness control
direct radiation through the thing being made (e.g paper) and put detecter on the other side, when amount detected changes it means thickness has changed so the control unit adjusts rollers, needs to have short half life and be beta so paper will partly block radiation, if all go through reading won’t change
How are gamma rays used to treat cancer
high doses kill all living cells, have to be careful and direct gamma rays right at cancer to minimise damage to healthy cells.
What do lower doses of ionisation do to cells
cause minor damage without killing cell
can give rise to mutant cells which divide uncontrollably (cancer)
