IB Physics SL E.3.13 Background Radiation

Practise correcting detector readings for background radiation, comparing count-rate uncertainty and explaining why background must be measured over an appropriate interval.

Syllabus
First assessment 2025
Objective
—
Level
SL

Exam points

  • subtract background count rate from the measured source-plus-background rate before decay analysis
  • convert background counts and time to the same rate units used for the source measurement
  • reduce fractional random uncertainty by measuring background for longer and repeating counts

E.3.13—Background radiation question 1

[Maximum number: 1]

An experiment is carried out to determine the count rate, corrected for background radiation, when different thicknesses of copper are placed between a radioactive source and a detector. The graph shows the variation of corrected count rate with copper thickness.

Figure for Question E.3.13—Background radiation question 1 — IB Physics SL

Outline how the count rate was corrected for background radiation.

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