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Quiz Chapter 6: Nuclear Physics

10 questions · Form 5 Physics Bab 6: Nuclear Physics

10 questions · plays in fullscreen

Full Question List & Answer Key

Prefer reading to quizzing? All 10 questions are listed below with the answer and explanation under each one.

1. Which sheet material is sufficient to completely stop alpha particles?

  1. A single sheet of paper
  2. 5 mm thick aluminium plate
  3. 10 cm thick concrete wall
  4. Lead container
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Answer: A

Alpha particles have low penetrating power and are absorbed by a thin sheet of paper.

2. The radiation detector best suited for measuring background radiation count in a laboratory is a:

  1. Gold-leaf electroscope
  2. Geiger-Müller (G-M) tube connected to a ratemeter
  3. Cloud chamber
  4. Diffusion chamber
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Answer: B

A Geiger-Müller (G-M) tube connected to a digital ratemeter or counter is standard for precise quantitative measurements of ionizing radiation.

3. Which equation correctly represents a nuclear fission reaction?

  1. ¹₄₆C -> ¹₄₇N + ⁰₋₁e
  2. ²₁H + ³₁H -> ⁴₂He + ¹₀n + Energy
  3. ²³⁵₉₂U + ¹₀n -> ¹₄¹₅₆Ba + ⁹²₃₆Kr + 3(¹₀n) + Energy
  4. ²²⁶₈₈Ra -> ²²²₈₆Rn + ⁴₂He
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Answer: C

Uranium-235 absorbing a neutron and splitting into Barium-141, Krypton-92, extra neutrons, and energy is a nuclear fission reaction.

4. When a Radon-222 nucleus ($^{222}_{86}Rn$) emits an alpha particle, what is the nucleon number and proton number of the daughter nucleus formed?

  1. Nucleon number = 218, Proton number = 84
  2. Nucleon number = 222, Proton number = 87
  3. Nucleon number = 218, Proton number = 85
  4. Nucleon number = 226, Proton number = 88
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Answer: A

Alpha emission removes 4 from nucleon number (222 - 4 = 218) and 2 from proton number (86 - 2 = 84).

5. What is the primary function of the MODERATOR in a nuclear fission reactor?

  1. To absorb excess neutrons and stop chain reaction
  2. To slow down fast-moving neutrons so they can cause further fission
  3. To prevent radioactive radiation leakage to the surroundings
  4. To cool down the reactor core liquid
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Answer: B

A moderator (e.g. graphite or heavy water) slows down fast neutrons to thermal speeds for efficient nuclear fission.

6. If a sample of radioactive material decays from 80 g to 10 g in 45 minutes, what is its half-life?

  1. 15 minutes
  2. 22.5 minutes
  3. 30 minutes
  4. 10 minutes
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Answer: A

80g -> 40g (1) -> 20g (2) -> 10g (3 half-lives). Total time = 45 min, so T_{12} = 453 = 15 minutes.

7. Which particle is emitted when a neutron inside an unstable nucleus transforms into a proton during radioactive decay?

  1. Alpha particle
  2. Beta particle
  3. Positron
  4. Neutrino
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Answer: B

In beta decay, a neutron breaks down into a proton and a high-speed electron (beta particle).

8. Which of the following radioactive emissions possesses the strongest ionizing power?

  1. Alpha particle
  2. Beta particle
  3. Gamma ray
  4. Neutron beam
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Answer: A

Alpha particles (+2 charge, largest mass) have the highest power to ionize surrounding gas molecules.

9. Gamma radiation is unaffected by both electric and magnetic fields because:

  1. It travels faster than light
  2. It carries no electrical charge
  3. Its mass is extremely heavy
  4. It undergoes total internal reflection
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Answer: B

Gamma rays are high-frequency electromagnetic waves with zero electric charge and zero rest mass.

10. In a nuclear reaction, the total mass before reaction is 235.0439 u and after reaction is 234.8215 u. What is the mass defect (Δm)?

  1. 0.2224 u
  2. 0.1224 u
  3. 0.3124 u
  4. 0.0224 u
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Answer: A

Mass defect Δm = 235.0439 u - 234.8215 u = 0.2224 u.

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