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CAIE IGCSE Physics 5.2.1 Detection of radioactivity Question Bank

Practise handling background radiation, detector readings, count rates, sources, and corrected decay data from tables and graphs.

Syllabus
2026–2028
Course
Physics 0625

Exam points

  • subtract background count rate from detector readings to find the source count rate
  • read a graph or counter display to determine background count in counts/s or counts/min

Covered syllabus points

5.2.1.1—What is meant by background radiation5.2.1.2—Sources that make a significant5.2.1.3—Ionising nuclear radiation can be5.2.1.4—Count rate measured in counts/s or5.2.1.5—Measurements of background radiation

5.2.1 Detection of radioactivity question 1

[Maximum number: 1]

In a laboratory a radiation detector displays a count rate of 16 counts/minute due to background radiation.

State what is meant by background radiation.

5.2.1 Detection of radioactivity question 2

[Maximum number: 1]

A radiation detector is set up in a laboratory where there are no radioactive samples.

On six separate occasions, the detector is switched on for 1.0 minute and the background count is recorded. The counts are:

232725242025\begin{array}{llllll} 23 & 27 & 25 & 24 & 20 & 25 \end{array}

Suggest a possible source for this background radiation.

5.2.1 Detection of radioactivity question 3

[Maximum number: 6]

Question (a)

(a)

Fig. 10.2 shows an electric door lock.

The slot in the door contains an unmagnetised iron bolt attached to a spring.
The slot in the door frame is empty. This slot is surrounded by the coils of a solenoid.
In Fig. 10.2 the door is unlocked. The spring is not stretched.

Fig. 10.2

Fig. 10.2

In Fig. 10.3 the door is locked. The spring is now stretched.

Fig. 10.3

Fig. 10.3

The bolt is initially in the position shown in Fig. 10.2.
Describe and explain what happens when

[ 6 ]

Question (i)

(i)

the switch S is closed,

[ 4 ]

Question (ii)

(ii)

the switch S is reopened.

[ 2 ]
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