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)

(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)

(iii) A suitable source of gamma radiation is the isotope caesium 137. Complete the following sentence by choosing the correct word from below.

electrons                      neutrons                   protons

An atom of caesium 137 has two more .............................................. 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)

(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)

(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)

(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)

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From Q1 P1 AQA June 2007 but now on P2 syllabus