Cameroon O-Level Nuclear Physics – Complete Revision Sheet 🌟

1. Introduction

Definition: Nuclear physics studies the structure, behavior, and reactions of atomic nuclei.

2. Types of Radiation

Radioactivity: The spontaneous emission of energy from unstable nuclei, in the form of alpha, beta, or gamma radiation.

2.1 Radiation Summary Table

Type Composition Charge Mass Penetration Ionizing Power Uses
Alpha (α) 2 protons + 2 neutrons +2 Heavy Low (stopped by paper/skin) Very high Smoke detectors, radiotherapy
Beta (β) Electron (β-) or Positron (β+) -1 / +1 Very small Moderate (stopped by aluminum) Moderate Medical tracers, thickness gauges
Gamma (γ) Photon (electromagnetic radiation) None None Very high (stopped by lead/concrete) Low Sterilization, medical imaging, cancer treatment

2.2 Radiation Penetration Diagram

Alpha Beta Gamma

Alpha stopped by paper, Beta by aluminum, Gamma by lead/concrete

3. Radioactive Decay

Definition: Unstable nuclei lose energy by emitting radiation. The number of nuclei decreases exponentially over time.

Half-life: Time taken for half of a radioactive sample to decay.

Formula: Remaining nuclei = Initial nuclei × (1/2)^(time / half-life)

Time Remaining nuclei

Exponential decay curve

3.1 Worked Example

Example: Sample contains 800 atoms, half-life 2 hours. Remaining after 4 hours?
Solution: 800 × (1/2)^(4/2) = 800 × 1/4 = 200 atoms

4. Nuclear Reactions

4.1 Fission

U-235 Ba-141 Kr-92

Fission releases neutrons and energy

4.2 Fusion

D T He n

Fusion of Deuterium and Tritium produces Helium, neutron, energy

5. GCE-Style Practice Questions

Q1: Differentiate alpha, beta, gamma radiation.
Answer: See the summary table above.
Q2: A sample has half-life 3 hours. Initial atoms = 640. How many remain after 9 hours?
Solution: 640 × (1/2)^(9/3) = 640 × (1/8) = 80 atoms
Q3: 1 g of U-235 releases 8×10^10 J when fission occurs. Energy released by 0.5 g?
Solution: 0.5 × 8×10^10 = 4×10^10 J
Q4: Name two uses of nuclear energy.
Answer: Power generation, medical treatment (radiotherapy)
Q5: Give one similarity and one difference between fission and fusion.
Answer: Similarity: Both release energy. Difference: Fission splits heavy nucleus, fusion combines light nuclei.