GCSE Questions: Radioactivity
Q2. Some types of food are treated with gamma radiation. Low doses of radiation slow down the ripening of fresh fruit and vegetables while higher doses of radiation kill the bacteria that make the food go off.
(a)
(i) What is gamma radiation?
(1 mark)
An electromagnetic wave OR electromagnetic radiation. 
(ii) Food packed in crates or boxes can be treated using this method. Why must a source that emits gamma radiation be used?
(1 mark)
Gamma radiation is very penetrating. It can penetrate the crate/box/packaging/food, (whereas alpha radiation and beta radiation are not penetrating enough).
(iii) A suitable source of gamma radiation is the isotope caesium 137. Complete the following sentence by choosing the correct word from the onles in the table below:
electrons |
neutrons |
protons |
An atom of caesium 137 has two more neutrons than an atom of caesium 135.
(1 mark)
(b) The diagram shows how a conveyor belt can be used to move food past the radioactive source.
(i) How do the concrete walls reduce the radiation hazard to workers outside the food treatment area?
(1 mark)
The concrete absorbs most of the gamma radiation before it reaches the workers.
(ii) Suggest one way that the dose of radiation received by the food could be increased other than by changing the radioactive source.
(1 mark)
Any one from:
decrease the speed of the conveyor belt
make the food do more than one circuit
move the food closer to the source of radiation
(c) Some people may not like the idea of eating food treated with radiation.
(i) What evidence could a food scientist produce to show that food treated with radiation is safe to eat?
(2 marks)
The food would need to be tested on human volunteers or on animals. Scientists could monitor their health and compare their health to a control group that had no irradiated food. If there was no evidence of measurable ill effects in those who had the irradiated food it would indicate that it was safe to eat.
(ii) The diagram shows the sign displayed on food treated with radiation.
Why is it important for people to know which foods have been treated with radiation?
(1 mark)
It is important that they can make their own decision about eating or not eating treated food. They may not want to eat it because of their religious or moral views.
(Total 8 marks)
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