EduNinjaA student is investigating the count rate of a radioactive substance.
How must he adjust his reading for the background count?
Add the background count to his reading.
Ignore the background count as it will not affect his reading.
Subtract the background count from his reading.
Take repeat readings to eliminate the background count.
A radiation detector in a laboratory is measuring background radiation.
Which row describes the readings and the cause?
readings
cause
vary with no pattern
background radiation is random
vary with no pattern
radiation detectors are unstable
slowly increase during the day
background radiation increases as temperature increases
slowly reduce during the day
background radiation decreases as temperature increases
A radioactive source is placed near a detector connected to a counter.
210 counts are recorded by the counter in 3 minutes.
The background count rate is 20 counts per minute (cpm).
What is the corrected count rate for the radioactive source?
50 cpm
70 cpm
190 cpm
270 cpm
The dashed line on the graph shows the decay curve recorded from a sample of a particular radioactive isotope. The count rate includes background radiation.
Which curve shows the corrected count rate for the decay?
A teacher holds a radioactive source near a detector.
The reading on the detector is 320 counts/min.
The detector is switched on again after the source has been removed and it shows a reading of 20 counts/min.
What is the counts/min solely due to the source and why is there a reading on the detector when there is no radioactive source present?
counts/min
due to the source
reason for reading
with no source
300
zero error on detector
300
background radiation
340
zero error on detector
340
background radiation
State two different sources of background radiation.
1
2
A radiation detector is placed on the bench in a laboratory. It detects a background count rate of 40 counts/minute.
State what is meant by background radiation. Suggest one source for it.
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:
Suggest a possible source for this background radiation.
Leaks in underground water pipes are detected using radioactive tracers. Fig. 10.1 shows a radiation detector above a water pipe.
Fig. 10.1
Before the radioactive tracer is added to the water, the detector measures the background radiation above the pipe. The average background radiation is 26 counts/minute.
Define background radiation.
Suggest one source of radiation that may make a significant contribution to the background count rate.
A radioactive tracer is added to the water. The counter in Fig. 10.1 shows the count rate in counts/minute above the leak in the water pipe.
Determine the count rate due to the tracer.
A radiation detector in a laboratory records a reading of 10 counts / min. There are no radioactive samples in the laboratory.
Explain why the radiation detector records a reading and suggest a possible source.
explanation
source