Quick Summary
Nuclear Physics studies the nucleus of the atom, radioactivity, isotopes, nuclear reactions, and the uses and risks of nuclear energy.
Key Definitions
- Nucleus: Central part of an atom containing protons and neutrons.
- Isotopes: Atoms of the same element with same atomic number but different mass numbers.
- Radioactivity: Spontaneous emission of radiations from unstable nuclei.
- Nuclear fission: Splitting of a heavy nucleus into lighter nuclei.
- Nuclear fusion: Combining of light nuclei to form a heavier nucleus.
Important Radiations
| Radiation | Nature | Penetrating Power |
|---|---|---|
| Alpha | Positively charged particles | Low |
| Beta | High-speed electrons | Medium |
| Gamma | Electromagnetic radiation | High |
Nuclear Fission
In nuclear fission, a heavy nucleus splits into smaller nuclei and releases energy. This process is used in nuclear reactors.
Nuclear Fusion
In nuclear fusion, light nuclei combine to form a heavier nucleus. This is the process that powers the Sun and stars.
Representing Nuclei and Isotopes
A nucleus is written as ᴬ𝐙X, where A = mass number (protons + neutrons) and Z = atomic number (protons).
Half-Life
Half-life (T½) is the time taken for half the atoms in a radioactive sample to decay. After each half-life the remaining quantity halves.
Worked Example — half-life
A sample of 80 g of a radioactive element has a half-life of 5 years. How much remains after 15 years?
Fission vs Fusion (worked comparison)
Fusion releases more energy per unit mass and produces less radioactive waste, but requires extreme temperature/pressure.
Applications
- Electricity generation in nuclear power plants
- Cancer treatment using radiation
- Food preservation
- Tracer studies in agriculture and medicine
- Smoke detectors and industrial testing
Safety Notes
Radioactive materials must be handled carefully because excessive radiation can damage living tissues. Shielding, distance, and limited exposure time are important safety principles.
Important Questions
One Mark
- Define isotope.
- What is radioactivity?
- Name one use of radioisotopes.
Two Marks
- Differentiate between fission and fusion.
- What are alpha, beta, and gamma radiations?
- Why is radiation safety important?
Five Marks
- Explain nuclear fission with applications.
- Compare alpha, beta, and gamma radiations.
- Describe uses and hazards of radioactivity.
Common Mistakes
- Confusing fission and fusion.
- Writing all radiations have the same penetrating power.
- Ignoring safety precautions in application answers.
- Mixing atomic number and mass number.
Revision Checklist
- Isotopes definition memorised
- Fission vs fusion differences prepared
- Alpha, beta, gamma comparison revised
- Uses and hazards listed
- Safety precautions revised