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A level: Radioactivity Questions

Q9.

(a) A radioactive source gives an initial count rate of 110 counts per second. After 10 minutes the count rate is 84 counts per second.

(background radiation = 3 counts per second)

(i) Give three origins of the radiation that contributes to this background radiation.

(ii) Calculate the decay constant of the radioactive source in s–1.

(iii) Calculate the number of radioactive nuclei in the initial sample assuming that the detector counts all the radiation emitted from the source.

(7 marks)

(b) Discuss the dangers of exposing the human body to a source of radiation. In particular compare the dangers when the source is held outside, but in contact with the body, with those when the source is placed inside the body.

(3 marks)

(Total 10 marks)