Atom 2 Flashcards
explain how radiation is used in smoke detectors
smoke detectors use alpha radiation
1) a weak source of alpha radiation is placed in the detector, close to the two electrodes
2) the source causes ionisation a current flows between the two electrodes
3) if there’s a fire, smoke will absorb the radiation- so the current stops and the alarm counts
explain how radiation is used in traders in medicine
traders in medicine are always short half life beta or gamma emitters
1) certain radioactive isotopes can be injected into people/swallowed
their progress around the body can be followed using an external detector.
computer coverts the reading to a display showing where the strongest reading is coming from
eg iodine-131 which is absorbed by the thyroid gland like iodine-127 but gives out radiation which can be detected to indicate whether the thyroid glad is taking in iodine as it should
all isotopes which are taken into the body must be gamma or beta emitters. so that the radiation passes out the body , so the radioactivity inside the patient disappears (ie have a short half life)
explain how radiation is used in radiotherapy
treats cancer using gamma rats
1) high doses of gamma rats will kill all living cells, they can be used to treat cancers
2) gamma rats have to be directed carefully at the right dosage to kill all cancer cells without damaging normal cells
3) a fair bit of damage to normal cells is inevitable and makes the patient feel ill. but if the cancer is successfully killed off in then it’s worth it
name some uses of radiation
smoke detectors
traces in medicine
radiotherapy
sterilisation of food and surgical instruments
how does radiation sterilise food and surgical instruments
using gamma rats
1) food can be exposed to high dose of gamma rats which will kill microbes so keep food fresh for longer (irradiation)
2) medical instruments can be sterilised in the same way by boiling them
what are the advantages of irradiation over boiling
- doesn’t involve high temperatures
so fresh apples or plastic instruments can be sterilised without damaging them
-food isn’t radioactive afterwards, so it’s safe to eat
BUT
the isotope needs to be a very strong emitter of gamma rays with a reasonably long half-life (several months) so it doesn’t need replacing often
what happened when Marie Curie discovered radioactive properties of radium in 1898
no one knew it was dangerous.
it was used to make glow in the dark watches and many watch dial painters developed cancer as a result
how does radiation harm living cells
alpha beta and gamma radiation enter living cells and collide with molecules.
these collisions cause ionisation which damages/destroys the molecules
lower doses= minor damage to cell without killing, can rise to mutant cells which divide uncontrollably (cancer)
higher doses- kill cell completely which causes radiation sickness
what does the extent of harmful damage depend on
- how much exposure you have to radiation
2. the energy and penetration of radiation, sick some types are more hazardous than others
what types of radiation are nose dangerous outside the body
outside the body beta and gamma are the most dangerous
because they can get inside to the delicate organs but alpha is less dangerous as it can’t penetrate the skin
what type of radiation is most dangerous inside the body
inside the body alpha is the most dangerous
this is because they do their damage in very localised areas. beta and gamma are less dangerous inside the body as they pass straight out without doing much damage
what are some safety precautions for radiation
- use radioactive sources for a short time, so exposure is kept to a minimum
- never allow contact with skin, handle with tongs
- keep source as far from the body as possible so less radiation hits you (especially alpha particles)
- avoid looking directly at it
- store radioactive sources in lead box and put them away asap. radiographer swear lead aprons and stand behind lead screens for protection (it absorbs radiation)
- when conducting an x-ray or radiotherapy only the part of body that needs to be treated is exposed to radiation, rest of body covered with radiation absorbing material
what was the harmful radiation effects of the atomic bomb in god japan in 1945
after the bombing thousands suffered radiation sickness - symptoms include nausea, fatigue, skin burns, hair loss or death
long term- area experienced increased rates of cancer particularly leukaemia
what is nuclear fission
te splitting up of big atomic nuclei
nuclear power stations generate electricity using nuclear reactors.
inside a chain reaction takes place where the atomic nuclei splits up and redorases energy in the form of heat.
the heat is used to heat water which makes streams this is used to drive a steam turbine connected to an electricity generator.
the fuel that’s split is usually uranium-235 or plutonium-239
explain the chain reaction in nuclear fission
for nuclear fission, a slow moving neutron must be absorbed into uranium/plutonium nucleus. this neutron makes the nucleus unstable - causing it to split
each time it splits, it spits out two or three neutrons, one of which may hit another nucleus causing t to split- keeping the chain reaction going
when a large atom splits it forms two smaller nuclei, which are usually radioactive because they have the ‘wrong’ number of neutrons
