DP Physics (first assessment 2025)

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Question SPM.2.SL.TZ0.c

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Date May Specimen-2023 Marks available [Maximum mark: 3] Reference code SPM.2.SL.TZ0.c
Level SL Paper 2 Time zone TZ0
Command term Calculate Question number c Adapted from N/A
c.
[Maximum mark: 3]
SPM.2.SL.TZ0.c

The initial activity of the source is 42 kBq. 33% of the alpha particles emitted by this source enter the chamber and form an ion pair.

Each alpha particle has an initial kinetic energy of 5.5 MeV.

The energy required to form one ion pair is 15 eV.

Calculate the maximum current in the chamber due to the electrons when there is no smoke in the chamber.

[3]

Markscheme

Each alpha gives rise to 5.5×10615=3.67×105 ion pairs ✓

So 3.67×105×420003=5.13×109 ion pairs per second ✓

current =1.6×10-19×5.13×109=0.82×10-9 «A» ✓

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