Edexcel IGCSEPhysicsGeneral Applications6 Marks
A sample of a radioactive isotope has a half-life of 6 hours.
- (a)Explain what is meant by the term 'half-life'.[2]
- (b)Initially, the activity of the sample is 800 Bq. Calculate the activity of the sample after 18 hours.[3]
- (c)State one safety precaution that should be taken when handling radioactive sources.[1]
Mark scheme
Marking points from the official mark scheme. The mark or mark type is shown in brackets.
- 3(a)
- B1 for (the) time taken for half the (unstable) nuclei/atoms to decay
- B1 for (the) time taken for the activity/count rate to halve
- 3(b)
- M1 for calculating number of half-lives: 18 / 6 = 3 (half-lives)
- C1 for showing sequential halving of activity (e.g., 800 -> 400 -> 200 -> 100)
- A1 for 100 Bq
- 3(c)
- B1 for use tongs / keep at arm's length / wear protective clothing (e.g., gloves, lead apron) / minimise exposure time / keep source in lead-lined container / store safely (Any one valid precaution)
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