Question 22M.2.SL.TZ2.5a
| Date | May 2022 | Marks available | [Maximum mark: 1] | Reference code | 22M.2.SL.TZ2.5a |
| Level | SL | Paper | 2 | Time zone | TZ2 |
| Command term | Outline | Question number | a | Adapted from | N/A |
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.
Outline how the count rate was corrected for background radiation.
[1]
background count rate is subtracted «from each reading» ✓
OWTTE
a) A majority of candidates were able to say that background radiation count was subtracted from all readings.
b) A fairly easy question with most candidates being able to take readings from the graph to get a final count rate of approximately 380 counts per second. Many did not seem to have used a ruler to help their reading.
c) This was a bit chaotic with candidates showing all sorts of misconceptions. The first marking point was the one most commonly awarded. The 2 big misconceptions were that the copper and lead were radioactive themselves and produced the radiation, or that the higher the figures the better absorbers they were. Far too many candidates thought that the question was only about the radiation passing through the 3.5 mm of lead and copper. Most of these candidates realised that there must be some gamma radiation in the radiation detected. Far fewer stated that there could not be any alpha. Opinions varied as to whether there was beta, but any sensible answers were given credit.
d) This question was generally well answered, with most candidates getting
