DP Physics (first assessment 2025)

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Question 22M.1A.SL.TZ1.26

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Date May 2022 Marks available [Maximum mark: 1] Reference code 22M.1A.SL.TZ1.26
Level SL Paper 1A Time zone TZ1
Command term Question number 26 Adapted from N/A
26.
[Maximum mark: 1]
22M.1A.SL.TZ1.26

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

[1]

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.

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