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Radioactivity Nuclear and decay — Free MYP4 Physics Practice Questions
1QuestionApplications of radioactivity in medicineConcept Practice
2 marks~3 minCriterion D
Positron Emission Tomography (PET) scanning uses the radioactive tracer fluorine-18 (F), which is incorporated into a glucose analogue and injected into a patient. Metabolically active tissues — such as tumours — absorb the tracer preferentially. As F undergoes beta-plus decay, the emitted positrons annihilate with electrons, producing pairs of gamma rays detected by the scanner to construct a functional image.
Explain how the mechanism of PET scanning makes it particularly useful for detecting cancerous tissue. [1]
Identify one safety consideration that must be addressed when using PET scanning on a patient. [1]
Explain how the mechanism of PET scanning makes it particularly useful for detecting cancerous tissue. [1]
Identify one safety consideration that must be addressed when using PET scanning on a patient. [1]
Solutions
2QuestionHalf-life DefinitionAssessment Practice
5 marks~8 minCriterion B
A student monitors a radioactive source, recording count rate every 30 s.
| Time (s) | 0 | 30 | 60 | 90 | 120 | 150 | 180 | 210 | 240 | 270 | 300 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Count rate (counts/s) | 800 | 566 | 400 | 283 | 200 | 141 | 100 | 71 | 50 | 35 | 25 |
a
Calculate the half-life of this isotope, showing clearly which data values you used. [1]
b
Show that the count rate data is consistent with exponential decay by demonstrating the halving pattern across at least four successive half-life intervals. [2]
c
Evaluate whether the full dataset provides convincing evidence that the decay constant remains unchanged throughout the 300 s observation period. Use the relationship in your reasoning. [2]
Solutions
3QuestionDecay series (basic idea)Concept Practice
2 marks~3 minCriterion A
The diagram shows part of the uranium-238 decay series:
a
Deduce the type of nuclear decay occurring at each of the three steps. [1]
b
Construct a balanced nuclear equation for each step, using correct nuclide notation for the parent nucleus, daughter nucleus, and emitted particle. [1]
Solutions
4QuestionHalf-life Interpretation of decay graphsAssessment Practice
6 marks~9 minCriterion A
A researcher monitors the mass of a radioactive isotope sample at regular intervals. The results are recorded below.
| Time (s) | 0 | 10 | 20 | 30 | 40 | 50 |
|---|---|---|---|---|---|---|
| Mass (g) | 80 | 56 | 40 | 28 | 20 | ? |
a
Deduce the half-life of this sample. Use the data to support your answer. [2]
b
Calculate the predicted mass at 50 s. Show your working clearly. [2]
c
A second sample of the same isotope has an initial mass of 160 g. Analyse whether the half-life of this second sample is different from the first. Justify your answer with reference to the nature of radioactive decay. [2]
Solutions
5QuestionApplications of radioactivity in Industry/ medicine / archaeology/biology/ meteorologyAssessment Practice
6 marks~9 minCriterion B
Archaeologists use the ratio of carbon-14 (parent) to nitrogen-14 (daughter) atoms in bone samples to estimate their age. The half-life of carbon-14 is 5730 years. Measurements from bone samples of known age are shown below.
| Sample age (years) | 0 | 5730 | 11 460 | 17 190 |
|---|---|---|---|---|
| Parent-daughter ratio | 1.00 | 0.50 | 0.25 | 0.125 |
a
Deduce the mathematical relationship between the parent-daughter ratio and the number of half-lives elapsed, using the data in the table to support your answer. [2]
b
Calculate the parent-daughter ratio for a bone sample that is 22 920 years old, and explain what this value tells an archaeologist about the remaining carbon-14 in the sample. [2]
c
A colleague claims that carbon-14 dating becomes unreliable beyond about 50 000 years because the parent-daughter ratio falls below a measurable threshold. Analyse this claim using the exponential decay model, and evaluate whether the data trend supports it. [2]
Solutions
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