Secondary 4 Pure Physics Modern Physics Quiz

Secondary 4 Pure Physics Quiz - Modern Physics

Name: ___________________________
Class: ___________________________
Date: ___________________________
Score: _______ / 40

Duration: 50 minutes
Total Marks: 40

Instructions:

• Answer all 20 questions.
• Section A: Multiple-choice style short responses (1 mark each).
• Section B: Structured questions requiring short calculations or explanations (2 marks each).
• Section C: Extended structured questions (3 marks each).
• Show your working where calculation is required.
• Use $g = 10\ \text{m/s}^2$ if needed.

Caveat: Past-year paper evidence for Modern Physics at Secondary 4 is very weak (≈0.2% of extracted blocks). This quiz is generated from syllabus-first LLM templates and is NOT derived from actual exam questions.

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Section A (Questions 1–5, 1 mark each)

1. What is the nature of alpha ($\alpha$) particles emitted during radioactive decay?

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2. State the unit used to measure background radiation dose equivalent.

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3. Which type of nuclear radiation is stopped completely by a few millimetres of aluminium?

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4. In the symbol $^{14}_{6}\text{C}$, what does the number 6 represent?

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5. Name the process by which a nucleus emits a helium nucleus.

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Section B (Questions 6–15, 2 marks each)

6. A radioactive source has an initial count rate of $800\ \text{s}^{-1}$ and a background count rate of $50\ \text{s}^{-1}$. Calculate the corrected initial count rate.

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7. The half-life of a substance is $4.0$ hours. If the initial number of nuclei is $2000$, how many nuclei remain after $12$ hours? Show your working.

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8. State one similarity and one difference between $\beta^-$ and $\beta^+$ radiation.
Similarity: __________________________________________________
Difference: __________________________________________________

9. A nucleus of $^{238}_{92}\text{U}$ emits one $\alpha$ particle. Write the resulting nuclide in the form $^A_Z\text{X}$.

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10. Explain why gamma ($\gamma$) rays are used for sterilising medical equipment.

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11. A sample has activity $A = 640\ \text{Bq}$ and decays with half-life $2.0$ s. What is the activity after $6.0$ s?

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12. The count rate near a source is measured as $120\ \text{s}^{-1}$ including background. If background is $20\ \text{s}^{-1}$, what is the corrected count rate?

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13. State the charge and approximate mass (in u) of a neutron.
Charge: ___________________ Mass: ___________________

14. A radioactive nucleus $^{210}_{84}\text{Po}$ decays by $\alpha$ emission. Calculate the atomic number of the daughter nucleus.

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15. Give one safety precaution when handling radioactive sources in school labs.

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Section C (Questions 16–20, 3 marks each)

16. A sample initially has $N_0 = 4800$ nuclei. Its half-life is $3.0$ minutes.
(a) Calculate the number of nuclei left after $9.0$ minutes.
(b) Explain why the count rate decreases exponentially rather than linearly.
(a) _________________________
(b) _______________________________________________________

17. The table shows count rates from a source over time.

Time (h)	Count rate (s⁻¹)
0	400
2	200
4	100

Background = $20\ \text{s}^{-1}$.
(a) Find the corrected count rate at $t = 0$.
(b) Determine the half-life.
(c) State the count rate at $t = 6$ h including background.
(a) _______ (b) _______ h (c) _______ s⁻¹

18. Compare the penetrating power of $\alpha$, $\beta$, and $\gamma$ radiation. Order them from least to most penetrating and state the absorber needed for each.

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19. A nucleus $^{60}_{27}\text{Co}$ undergoes $\beta^-$ decay.
(a) Write the daughter nuclide.
(b) Explain what happens to the neutron during this decay.
(a) ___________________
(b) _______________________________________________________

20. A radioactive source has half-life $T_{1/2} = 5.0$ days and initial activity $A_0 = 1000\ \text{Bq}$.
(a) Calculate the activity after $15$ days.
(b) State one practical use of radioactive tracers in medicine.
(a) _______ Bq
(b) _______________________________________________________