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5.2 Radioactivity

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Question 9

A student holds a radioactive source near a radiation detector.

The reading on the detector is 450 counts/min450\text{ counts/min}450 counts/min.

The detector is switched on again after the source has been removed, and it shows a reading of 25 counts/min25\text{ counts/min}25 counts/min.

What is the count rate solely due to the source, and why is there a reading on the detector when there is no radioactive source present?

A

Count rate: 425 counts/min425\text{ counts/min}425 counts/min; Reason: background radiation

B

Count rate: 425 counts/min425\text{ counts/min}425 counts/min; Reason: zero error on detector

C

Count rate: 475 counts/min475\text{ counts/min}475 counts/min; Reason: background radiation

D

Count rate: 475 counts/min475\text{ counts/min}475 counts/min; Reason: zero error on detector

Markscheme

5.2 Radioactivity Questions

  1. IGCSE
  2. /Physics
  3. /5.2 Radioactivity

484 exam-style questions on CIE IGCSE Physics 5.2 Radioactivity, covering 5.2.1 Background radiation and measuring count rate, 5.2.2a Alpha, beta and gamma emission, 5.2.2b Deflection and ionising effects of nuclear radiation, 5.2.3a Radioactive decay, 5.2.3b Effects of decay on the nucleus and decay equations, 5.2.4a Half-life, 5.2.4b Choosing isotopes for applications, and 5.2.5 Effects of ionising radiation and safety precautions. Each one has a worked solution and a mark scheme showing where the marks go.

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