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
Why do radiotherapy patients feel ill?
- directed carefully at the right dosage, to kill cancer cells without damaging to many normal cells
- damage to normal cells is inevitible, and make patients feel very ill
Give an example of a tracer used in medicine.
- iodine-123, is absorbed by thyroid gland
- gives out radiation which can be detected to indicate whether or whether not the thyroid is taking in iodine as it should
How is radon gas formed, is it dangerous and what precautions can be taken?
-granite contains lots of uranium
uranium decays into radon gas which emits alpha particles
-although alpha particles are not very penetrating, radon is a gas and so we inhale the alpha particles which are highly ionising
-a high exposure of radon gas can lead to lung cancer
-to ensure gas doesn’t build up in your house:use extractor fans or vented floors (new buildings in high radon areas) to draw gas out before it can enter your home, impenetrable damp-proof membranes on ground floor
What does the amount of background radiation depend?
- where you are, e.g.what type of rock your hosue is built on (some rocks are more radiative than others)
- your job, e.g. working in an industry that uses radiation
What does the amount of background radiation depend?
- where you are, e.g.what type of rock your hosue is built on (some rocks are more radiative than others)
- your job, e.g. working in an industry that uses radiation
Why is gamma radiation used in industry?
- so radiation can be detected even though metal and earth which may be surrounding pipes (when finding leaks)
- alpha and beta would be blocked by any surrounding material
