Question
When measuring the emissions from a radioactive rock brought into the laboratory, a teacher
mentions that background radiation must be taken into account. 5.2.1
What is this background radiation?
A infra-red radiation from warm objects in the laboratory
B infra-red radiation from the Sun
C ionising radiation from the radioactive rock brought into the laboratory
D ionising radiation in the laboratory when the radioactive rock is not present
Answer/Explanation
Ans: D
Question
A student measures the level of radiation emitted from a radioactive substance. He places a
detector very close to the substance. He puts different absorbers between the radioactive
substance and the detector.
The student’s results are shown. These results are corrected for background radiation.
absorber | counter reading counts per minute |
none | 95 |
thin paper | 52 |
few mm of aluminium | 52 |
several cm of lead | 12 |
Which types of radiation are being emitted by the substance?
α-particles and β-particles only
α-particles and γ-rays only
β-particles and γ-rays only
α-particles, β-particles and γ-rays
Answer/Explanation
Ans: B
Question
The diagram shows the paths of three different types of radiation, X, Y and Z.
Which row in the table correctly identifies X, Y and Z?
| X | Y | Z |
A | α-particles | β-particles | γ-rays |
B | β-particles | α-particles | γ-rays |
C | β-particles | γ-rays | α-particles |
D | γ-rays | α-particles | β-particles |
Answer/Explanation
Ans: B
Question
In a laboratory, a detector of ionising radiation records an average background count rate of
8 counts per second.
A radioactive source is now placed close to the detector. The count rate on the detector rises to
200 counts per second.
What is the count rate due to radiation from the radioactive source?
A 25 counts / s
B 192 counts / s
C 200 counts / s
D 208 counts / s
Answer/Explanation
Ans: B
Question
The arrangement shown is used to check whether the flour inside a cardboard packet is above a
certain level. If it is above this level, the flour absorbs the radiation from the source so that it
doesn’t reach the detector.
Which type of radiation is suitable to use?
A. α-particles only
B.β-particles only
C. either α-particles or β-particles
D. γ-rays only
Answer/Explanation
Ans: B