Atomic and Nuclear Physics explores the structure of the atom, radioactivity, and nuclear reactions. This chapter explains atomic models, properties of alpha, beta, and gamma radiations, half-life, nuclear fission, and fusion. It also discusses the uses of nuclear energy, radiation hazards, and safety measures.
1. Who discovered the electron?
- A. J.J. Thomson ✅
- B. Rutherford
- C. Bohr
- D. Chadwick
Explanation: J.J. Thomson discovered the electron in 1897 using cathode ray experiments.
2. Which subatomic particle carries a positive charge?
- A. Proton ✅
- B. Neutron
- C. Electron
- D. Positron
Explanation: Protons are positively charged particles located in the nucleus of an atom.
3. Who proposed the nuclear model of the atom?
- A. Rutherford ✅
- B. Bohr
- C. Thomson
- D. Dalton
Explanation: Rutherford’s gold foil experiment revealed the presence of a small, dense nucleus.
4. Who discovered the neutron?
- A. James Chadwick ✅
- B. Rutherford
- C. Thomson
- D. Bohr
Explanation: James Chadwick discovered the neutron in 1932, a neutral particle in the nucleus.
5. The nucleus of an atom consists of:
- A. Protons and neutrons ✅
- B. Protons and electrons
- C. Neutrons and electrons
- D. Electrons only
Explanation: Protons and neutrons, collectively called nucleons, are found in the nucleus.
6. Which type of radiation has the greatest penetrating power?
- A. Gamma rays ✅
- B. Alpha particles
- C. Beta particles
- D. Neutrons
Explanation: Gamma rays are high-energy electromagnetic waves with very high penetration.
7. Which radiation can be stopped by a sheet of paper?
- A. Alpha particles ✅
- B. Beta particles
- C. Gamma rays
- D. Neutrons
Explanation: Alpha particles have low penetration and can be blocked by paper or skin.
8. Which type of radiation is deflected by electric and magnetic fields?
- A. Alpha and beta particles ✅
- B. Gamma rays only
- C. Neutrons only
- D. X-rays only
Explanation: Alpha (positive) and beta (negative) particles are charged and deflected by fields.
9. The unit of radioactivity is:
- A. Becquerel ✅
- B. Gray
- C. Sievert
- D. Joule
Explanation: One becquerel equals one nuclear disintegration per second.
10. Half-life is the time taken for:
- A. Half the radioactive nuclei to decay ✅
- B. All nuclei to decay
- C. Radiation to stop
- D. The atom to split
Explanation: Half-life measures how quickly a radioactive substance decays.
11. Which equation relates mass and energy?
- A. E = mc² ✅
- B. F = ma
- C. V = IR
- D. P = IV
Explanation: Einstein’s equation shows the equivalence of mass and energy.
12. Which reaction powers the Sun?
- A. Nuclear fusion ✅
- B. Nuclear fission
- C. Chemical reaction
- D. Combustion
Explanation: Fusion combines hydrogen nuclei into helium, releasing huge energy.
13. In nuclear fission, a heavy nucleus splits into:
- A. Two lighter nuclei and energy ✅
- B. One heavier nucleus
- C. Three protons
- D. Neutron only
Explanation: Fission releases energy and free neutrons.
14. In a chain reaction, neutrons released cause:
- A. Further fission reactions ✅
- B. Cooling of the reactor
- C. Radiation shielding
- D. Reduction in energy
Explanation: A chain reaction continues when released neutrons cause further fissions.
15. Which isotope is commonly used as nuclear fuel?
- A. Uranium-235 ✅
- B. Carbon-14
- C. Plutonium-239
- D. Thorium-232
Explanation: Uranium-235 undergoes fission easily with slow neutrons.
16. Which device measures radiation levels?
- A. Geiger-Müller counter ✅
- B. Ammeter
- C. Voltmeter
- D. Galvanometer
Explanation: GM counters detect ionizing radiation using a gas-filled tube.
17. Which device controls the rate of fission in a nuclear reactor?
- A. Control rods ✅
- B. Turbines
- C. Generators
- D. Coolants
Explanation: Control rods absorb neutrons to control fission rate.
18. The moderator in a nuclear reactor is used to:
- A. Slow down neutrons ✅
- B. Increase neutron speed
- C. Absorb radiation
- D. Cool the reactor
Explanation: Moderators like graphite slow neutrons for sustained fission.
19. What is critical mass?
- A. Minimum fissile mass for a chain reaction ✅
- B. Maximum safe fuel mass
- C. Core weight
- D. Rod mass
Explanation: Below critical mass, a chain reaction cannot be sustained.
20. Which byproduct of nuclear fission is highly radioactive?
- A. Strontium-90 ✅
- B. Oxygen-16
- C. Carbon-12
- D. Helium-4
Explanation: Strontium-90 is hazardous and must be handled carefully.
21. Which material is best for shielding gamma rays?
- A. Lead ✅
- B. Wood
- C. Plastic
- D. Aluminium
Explanation: Lead’s high density makes it effective against gamma rays.
22. What is the main drawback of nuclear power plants?
- A. Radioactive waste disposal ✅
- B. Low energy output
- C. High fuel cost
- D. Inefficient conversion
Explanation: Waste remains dangerous for thousands of years.
23. Which famous nuclear disaster occurred in 1986?
- A. Chernobyl ✅
- B. Fukushima
- C. Three Mile Island
- D. Windscale
Explanation: Chernobyl caused massive radioactive contamination.
24. Which country conducted the first controlled nuclear chain reaction?
- A. USA ✅
- B. Russia
- C. Japan
- D. UK
Explanation: The first controlled chain reaction was in Chicago in 1942.
25. In beta decay, a neutron changes into:
- A. A proton and an electron ✅
- B. A proton only
- C. An electron only
- D. A gamma ray
Explanation: Beta decay emits an electron and converts a neutron into a proton.
26. Which scientist discovered radioactivity?
- A. Henri Becquerel ✅
- B. Marie Curie
- C. Rutherford
- D. Einstein
Explanation: Becquerel discovered natural radioactivity in 1896.
27. Who discovered polonium and radium?
- A. Marie and Pierre Curie ✅
- B. Thomson and Rutherford
- C. Bohr and Einstein
- D. Fermi and Chadwick
Explanation: The Curies discovered polonium and radium, contributing to nuclear science.
28. Which type of nuclear reaction occurs in the Sun?
- A. Fusion ✅
- B. Fission
- C. Alpha decay
- D. Beta decay
Explanation: The Sun fuses hydrogen into helium, producing energy.
29. Which is the main safety concern in a nuclear plant?
- A. Reactor core meltdown ✅
- B. Low fuel supply
- C. Overproduction
- D. Water shortage
Explanation: A meltdown releases dangerous radiation into the environment.
30. Which nuclear disaster happened in Japan in 2011?
- A. Fukushima ✅
- B. Chernobyl
- C. Three Mile Island
- D. Kyshtym
Explanation: Fukushima was caused by a tsunami damaging the nuclear plant.