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Date May 2022 Marks available 1 Reference code 22M.1.SL.TZ1.26
Level Standard level Paper Paper 1 Time zone 1
Command term Question number 26 Adapted from N/A

Question

The background count in a laboratory is 20 counts per second. The initial observed count rate of a pure sample of nitrogen-13 in this laboratory is 180 counts per second. The half-life of nitrogen-13 is 10 minutes. What is the expected count rate of the sample after 30 minutes?

A.  20 counts per second

B.  23 counts per second

C.  40 counts per second

D.  60 counts per second

Markscheme

C

Examiners report

Option B was the most frequent answer, incorrectly selected by candidates who did not consider the background count in the laboratory.

Syllabus sections

Core » Topic 7: Atomic, nuclear and particle physics » 7.1 – Discrete energy and radioactivity
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Core » Topic 7: Atomic, nuclear and particle physics
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