Section 7 Flashcards
How can we detect ionising radiation?
Photographic film or a Geiger-Muller detector.
What are alpha particles?
Helium nuclei
What does emitting an alpha particle do to an atom?
Decrease the atomic number of the nucleus by 2 and the mass number by 4.
What are beta particles?
Electrons
What do beta particles do to an atom when released?
Increase the atomic number by 1 and the mass number remains the same.
What are gamma rays?
Very short wavelength EM waves.
How can alpha be blocked?
Paper, skin.
How can beta particles be stopped?
Thin metal.
How can gamma rays be stopped?
Thick lead or very thick concrete.
When being shot through a substance what happens if the alpha particle is travelling fast?
The less it will be deflected by the nucleus.
What will happen to an alpha particle if the nucleus is more positively charged?
The more the alpha particle will be deflected.
What is a half life?
The time taken for half of the radioactive atoms now present to decay.
What makes beta and gamma suitable for medical tracers?
They will penetrate the skin and other body tissues.
Why is gamma used in industrial tracers?
So the radiation can be detected through any rocks or earth surrounding the pipe.
Why does the gamma have to have a short life when being used in industrial tracers?
So not to cause a long-term hazard if it collects somewhere.
How can gamma show if there is a crack in the pipe?
The gamma source will collect outside the pipe, where the crack is, and the detector will show extra high radioactivity at that point.
In medical tracers why does the radioactive source need to have a short half-life?
So you can use less of the radioactive source but still get a reading on your detector.
How can you see how old an object is?
By measuring the amount of radioactive isotope left in the sample, and knowing the half-life, you can work out how long the object has been around.
What can low doses of alpha cause?
They don’t kill cells but can cause mutations in cells which then divide uncontrollably - this is cancer.
What do higher doses of alpha do?
Tend to kill cells completely, causing radiation sickness if a large part of the body is affected at the same time.
The harmful effects of alpha depend on what?
How much exposure you have to the radiation, its energy and penetration.
How does radiotherapy work?
It involves a high dose of gamma rays and kills the cancer cells preventing them dividing.
How people who work with radioactive sources stay safe?
Wear lead aprons, use remote-controlled robot arms when handling the sources.
What is nuclear fission?
The splitting of an atom, which releases energy.
