QUARTER FINAL STAGE 2026
Achimota School: 55 points
Adisadel College: 28 points
Boa Amponsem SHS: 23 points
QUESTION
Which of the following is an economic importance of the study of nuclear and particle physics?
Brachytherapy, muon tomography, oil well logging, and single photon emission computed tomography (SPECT).
ANSWER: All of them
SOLUTION:
All four are real, economically important applications of nuclear/particle physics:
Brachytherapy — the placement of radioactive sources inside or next to tissue to treat cancer.
Muon tomography — using naturally occurring cosmic-ray muons to image large, dense structures (e.g. pyramids, volcanoes, reactor cores) non-invasively.
Oil well logging — using radioactive/nuclear tools for geological surveying to locate oil deposits.
SPECT — a nuclear medicine imaging technique using gamma-emitting radioisotopes.
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PRACTICE QUESTIONS
1. QUESTION: Name the cancer treatment in which a sealed radioactive source is placed inside or next to a tumour.
ANSWER: Brachytherapy
SOLUTION:
The source delivers a high dose to the tumour and little to healthy tissue.
2. QUESTION: Name the medical imaging technique that detects pairs of gamma photons produced when positrons annihilate with electrons.
ANSWER: Positron emission tomography (PET)
SOLUTION:
A positron-emitting tracer is injected, and the gamma-ray pairs locate it.
3. QUESTION: Which radioisotope is commonly used to date archaeological remains of once-living things?
ANSWER: Carbon-14
SOLUTION:
Living things take in carbon-14; after death it decays with a half-life of about five thousand seven hundred years.
4. QUESTION: What particles from cosmic rays are used in tomography to image the inside of pyramids and volcanoes?
ANSWER: Muons
SOLUTION:
Muons penetrate deep into matter, and their absorption reveals dense regions.
5. QUESTION: How are gamma rays used to preserve food?
ANSWER: They kill bacteria and other microorganisms in the food (food irradiation).
SOLUTION:
The food does not become radioactive.
6. QUESTION: How do radioactive tracers help detect leaks in underground pipes?
ANSWER: A gamma-emitting tracer is added to the fluid, and a detector above ground finds where it collects.
SOLUTION:
The tracer concentrates where the fluid escapes.
7. QUESTION: Which type of radiation is used to control the thickness of paper in a factory?
ANSWER: Beta radiation
SOLUTION:
Beta particles are partly absorbed by paper, so the detected count shows the thickness.
8. QUESTION: Which radioisotope is used in most household smoke detectors?
ANSWER: Americium-241
SOLUTION:
Its alpha particles ionise air in a chamber; smoke reduces the current and sets off the alarm.
9. QUESTION: How is nuclear fission used economically?
ANSWER: To generate electricity in nuclear power stations.
SOLUTION:
Fission of uranium releases large amounts of energy that heats water to drive turbines.
10. QUESTION: Why is cobalt-60 used to sterilise medical equipment?
ANSWER: Its gamma rays kill microorganisms, even through sealed packaging.
SOLUTION:
Gamma rays are highly penetrating.
11. QUESTION: Name the nuclear imaging technique that uses a gamma camera to detect single gamma photons from a tracer.
ANSWER: Single photon emission computed tomography (SPECT)
SOLUTION:
A rotating gamma camera builds a three-dimensional image from the tracer's gamma rays.
12. QUESTION: How are radioactive sources used in oil well logging?
ANSWER: Neutron or gamma sources lowered into a borehole reveal the rock layers and where oil or water lies.
SOLUTION:
The returned radiation depends on the composition of the surrounding rock.