DULWICH COLLEGE SHANGHAI
SCIENCE DEPARTMENT
NAME:______DATE:______
IGCSE - PHYSICS
Nuclear Physics
Answer all questions in the spaces provided.
Use full working for all calculations.
1. In an atom of 235U92, after absorption of a slow neutron, undergoes fission to form an atom of 138Ba56and an atom of 95Kr36. What other particles are produced? Write a balanced nuclear equation for this process.
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3 MARKS
2. (a) Food - irradiation is an effective way of sterilising food. The radiation kills the bacteria that cause food to decay or spoil. 10 kilograys (kGy) of gamma - ¡ - radiation is enough to sterilise food. Which type of radiation is most appropriate for this task? Explain in detail the reasoning for your answer.
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2 MARKS
2. (b) Give two reasons for your answer in 2 (a).
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2 MARKS
3. (a) The diagnosis of blood disorders can be made using a radioactive nuclide of Fe. A sample of this nuclide is found to have 50 % of its atoms decayed by β emission after a 45-day period. What FRACTION of the sample remains undecayed after 6 months (180 days) after its initial use?
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2 MARKS
3. (b) Graphically represent the rate of decay of the sample over the 6 months.
3 MARKS
4. With the aid of a diagram explain what is meant by an uncontrolled nuclear chain reaction.
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4 MARKS
5. Complete the below nuclear equations by inserting the correct particle or radiation.
(a) 14N7 + 1n0 → 14C6 + ______
(b) 209Po84 → ______+ 0 e-1
(c) 1H1 + 2H1 → 3He2 + ______
(d) 238U92 → 234Th90 + ______
(e) 1n 0 + 10 B 5 → 7Li3 + ______
5 MARKS
6. (a) Explain the function of control rods in a nuclear reactor.
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2 MARKS
(b) Explain the function of moderators in a nuclear reactor.
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2 MARKS
7. Give two reasons why the disposal of the waste from Nuclear Reactors is such a difficult process.
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2 MARKS
8. Complete the below table concerning the different types of radiation.
Particle / Symbol / Nature / Ionising Ability / Charge / PenetrationAlpha / a
Beta / Moderate / - 1 / 2/3 sheets of Aluminium Foil
Gamma / ¡ / Ray / 30cm of Lead or Concrete
8 MARKS
9. Explain what is meant by the ionizing ability of a radioactive particle.
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2 MARKS
10. Explain why, when a Geiger Mueller Tube is turned on, it will register radioactivity being present when no obvious source is in the area?
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2 MARKS
11. Carbon – 14 is a radioactive isotope of Carbon that has a half-life of 5700 years. It tends to have a stable rate of decay in living organisms of 16Bq. A sample from a wooden figure dug up from an archeological dig near Beijing was found to have a decay rate of 4Bq. Determine the age of the sample.
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4 MARKS
12. “Beta radiation is more penetrating than alpha radiation but the alpha radiation causes more ionisation.”
What are two reasons why alpha particles have a greater ionising capacity than beta particles?
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13. The diagram below shows the arrangement by Geiger and Marsden to investigate the deflection of alpha particles when fired at thin gold foil.
(a) Explain why the experiment was carried out in a vacuum.
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2 MARKS
(b) The alpha source was surrounded by lead shielding with a long narrow opening in front of it. Suggest two reasons for this.
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2 MARKS
(c) The majority of the alpha particles went straight through the gold foil. What conclusions about the structure of the atom did Geiger and Marsden take from this observation?
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1 MARK
(d) How did Geiger and Marsden determine that the alpha particles were hitting the scintillation counter?
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1 MARK
(d) Geiger and Marsden observed that some alpha particles deviated as they passed through the gold foil. Describe the conclusions that they reached from this observation.
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2 MARK
(e) Geiger and Marsden noted that some alpha particles deviated further than others. Give two reasons for these observations.
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2 MARKS
End of Paper