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Nuclear decay test with answers for AP Physics 2 (free PDF download)

Quick answer: Atoms have discrete energy levels, so they emit and absorb photons of fixed energy equal to the gap between levels. This AP Physics 2 test on nuclear decay has 8 questions worth 20 marks, to do in 40 minutes: hydrogen transition, absorption and alpha decay. The mark scheme is on a separate page; free printable PDF.

Nuclear decay test with answers for AP Physics 2 (free PDF download)

This test covers energy levels, nuclear equations, half-life and binding energy with calculations and short explanations. Use 1 u = 931.5 MeV and hc = 1240 eV·nm where needed. Show each step.

Level: AP Physics 2 (algebra-based) · Curriculum: AP P2 Unit 15

Time: 40 minutes · 8 questions · Total: 20 marks · Calculator allowed

Question 1 Hydrogen transition (3 marks)

The diagram shows hydrogen levels.
Energy levels of hydrogen with n equal to 1, 2, 3 and 4 and three downward transitions0n = 4 -0.85 eVn = 3 -1.51 eVn = 2 -3.4 eVn = 1 -13.6 eV3 to 2: 1.89 eV, 656 nm4 to 2: 2.55 eV, 486 nm2 to 1: 10.2 eV, 122 nm
Hydrogen energy levels with three emission transitions.
An electron falls from n = 3 to n = 1. Use hc = 1240 eV·nm.
  1. Calculate the photon energy. (1 mark)
  2. Calculate the wavelength. (1 mark)
  3. State the region of the spectrum. (1 mark)

Question 2 Absorption (2 marks)

A hydrogen atom in the ground state is hit by photons of energy 10.2 eV and 10.0 eV.
  1. State which photon is absorbed. (1 mark)
  2. Explain your choice. (1 mark)

Question 3 Alpha decay (2 marks)

Polonium-210 (Z = 84) emits an alpha particle and becomes lead (Z = 82).
  1. Write the nuclear equation. (1 mark)
  2. Name the two quantities that are conserved in the equation. (1 mark)

Question 4 Beta decay (2 marks)

Iodine-131 (Z = 53) decays by beta minus emission to xenon.
  1. State the mass number and atomic number of xenon. (1 mark)
  2. Describe what happens inside the nucleus. (1 mark)

Question 5 Half-life calculation (3 marks)

A sample contains 40 mg of an isotope with half-life 12 hours.
  1. Calculate the mass left after 36 hours. (2 marks)
  2. Calculate the time for the mass to fall to 2.5 mg. (1 mark)

Question 6 Decay graph (3 marks)

The graph shows the count rate of a source.
A graph of count rate against time for a source falling from 800 to 400 after 6 hours, 200 after 12 hours, 100 after 18 hours and 50 after 24 hours061218240200400600800t (hours)count rate (per minute)
Count rate against time.
  1. Read the half-life. (1 mark)
  2. Predict the count rate at 18 hours. (1 mark)
  3. Explain why the rate at 12 hours is not zero. (1 mark)

Question 7 Mass defect (3 marks)

In a nuclear reaction the total mass decreases by 0.0150 u. Use 1 u = 931.5 MeV.
  1. Calculate the energy released in MeV. (1 mark)
  2. Convert this to joules, given that 1 MeV = 1.60 × 10⁻¹³ J. (1 mark)
  3. State the relationship used. (1 mark)

Question 8 Fusion and fission (2 marks)

Binding energy per nucleon peaks near iron-56.
  1. Explain why fusing light nuclei releases energy. (1 mark)
  2. Explain why splitting very heavy nuclei releases energy. (1 mark)

See the nuclear decay test answers and mark scheme

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