P4d Flashcards
What radiation is the most dangerous outside the body and why?
- beta and gamma
- because they can still get inside to organs because they pass through skin
What radiation is most dangerous inside the body and why?
- alpha
- because they do all their damage in a localised area
- beta and gamma are less ionising, and most pass through without doing much damage
How are alpha particles good ionisers?
- relatively large (so it’s easy for them to collide with atoms or molecules)
- highly charged (so they can easily removed electrons from atoms they pass or collide with)
How do different doses of ionising radiation affects a cell?
- higher does kill cells completely which causes radiation sickness if a lot of cells are blasted at the same time
- lower doses cause minor damage without killing the cells. Can give rise to mutant cells which divide uncontrollably, cancer
How do beta particles affect atoms?
- remove electrons as they pass or hit, leaving them positively charged
- a beta particle (electron) can also stick to atom, ionising it and making it negatively charged
How do alpha particles affect atoms?
-remove electrons as they pass or hit, leaving them positively charged
How do x-rays and gamma rays affect electrons?
- transfer energy to electrons
- electrons then have enough energy to escape from atom
- ionising it and leaving it positively charged
Describe x rays.
-similar properties to gamma rays as they have similar wavelength
-pass through flesh easily, but not so easily through thicker, denser materials like bone and metal
the thicker or denser the material, the more x-ray that’s absorbed
so the varying amount of radiation absorbed or not absorbed that makes an x ray image
-produced by firing high-speed electrons at a heavy metal like tungsten
-much easier to control than gamma rays
Describe gamma rays.
- similar properties to gamma rays as they have similar wavelength
- released from unstable atomic nuclei when they decay
- nuclear decay is random, so there is no way to control when they are released
How is radiotherapy used to treat cancer?
1-gamma rays focuses on the tumour using a wide beam
2-beam in rotated round the patient with the tumour at the centre
-this minimises exposure to normal cells, and so reduces chances of damaging the rest of the body
How are tracers used in medicine?
-certain radioactive isotopes that emit gamma (and sometimes beta), with short half-lives (few hours) are used as tracers in the body
1-injected into the body, drunk or eaten or ingested
2-allowed to spread through body
3-their progress is followed on radiation detectors outside
How are tracers used in industry?
used to find leaks in pipes
-same technique used in medicine
1-gamma radiation put into pipes
2-progress tracked with detector above ground or outside pip
3-leak is shown by a reduction of radiation, blockage is shown by no radioactivity after the point of blockages
-source should have a short half-life, so as to not cause a hazard if it collects somewhere
How is radiation used to sterilise medical equipment?
- sterilised by exposing to high dose of gamma rays, which kills all microbes
- doesn’t involve high temperatures like boiling, so heat-sensitive things like thermometers and plastic instruments can be totally sterilised without damaging them
How is radiation used in smoke detectors?
- weak alpha sources placed in detector close to two electrodes
- source ionises the air particles which allows a current to flow
- if there is a fire, smoke particles are hit by the alpha particles used
- this causes less ionisation of the air particles
- so the current is reduced causing the alarm to sound
Where does background radiation come from?
many sources
- large proportion from natural sources: food, air, building materials, rocks, radiation from space known as cosmic rays (mostly from sun)
- human activity (very small): fallout from nuclear weapons, water from industry or hospitals
