⭐ Modern Physics GK – Quantum, Relativity, Nuclear Science (50 Important Questions & Answers)
Modern Physics includes three major branches—Quantum Mechanics, Theory of Relativity, and Nuclear Physics. These topics frequently appear in SSC, Railway, Banking, Defence, UPSC, NDA, CDS, and State PSC exams.
Below are the 50 most important Modern Physics GK Questions with answers and explanations.
📘 50 Modern Physics GK Questions with Answers (With Explanation)
1. Who is known as the Father of Modern Physics?
Answer: Albert Einstein
Explanation: His contributions to Relativity and Quantum Theory revolutionised Physics.
2. Who proposed the theory of relativity?
Answer: Albert Einstein
Explanation: Includes Special and General Relativity.
3. E = mc² represents what?
Answer: Mass-energy equivalence
Explanation: Proposed in Special Relativity.
4. What is the speed of light considered as in relativity?
Answer: The ultimate speed limit of the universe.
Explanation: Nothing can travel faster than light.
5. Who introduced the idea of quantum energy packets?
Answer: Max Planck
Explanation: Called energy quanta or photons.
6. What is a photon?
Answer: A particle of light.
Explanation: Has no mass, travels at light speed.
7. Who discovered the electron?
Answer: J.J. Thomson
Explanation: Through cathode ray experiment.
8. Who discovered the neutron?
Answer: James Chadwick
Explanation: Discovered in 1932.
9. Who discovered the proton?
Answer: Ernest Rutherford
Explanation: Through gold foil experiment.
10. Nuclear energy is obtained from what?
Answer: Fission or fusion reactions.
Explanation: Conversion of mass into energy.
11. Which isotope is used in nuclear reactors?
Answer: Uranium-235
Explanation: Used in fission.
12. What is nuclear fission?
Answer: Splitting of a heavy nucleus.
Explanation: Releases huge energy.
13. What is nuclear fusion?
Answer: Joining of light nuclei to form heavier ones.
Explanation: Occurs in the sun.
14. Which particle has zero rest mass?
Answer: Photon
Explanation: Moves at light speed.
15. What does the Heisenberg Uncertainty Principle state?
Answer: You cannot know position and momentum simultaneously with perfect accuracy.
16. Who proposed the uncertainty principle?
Answer: Werner Heisenberg
17. What is the dual nature of light?
Answer: Wave + Particle
Explanation: Light behaves as both wave and particle.
18. Who discovered radioactivity?
Answer: Henri Becquerel
Explanation: Observed natural radiation from Uranium.
19. Who discovered the nucleus of the atom?
Answer: Rutherford
Explanation: Gold foil alpha-scattering experiment.
20. Who discovered the atomic model with energy levels?
Answer: Niels Bohr
Explanation: Proposed quantized orbits.
21. Which rays have the highest penetrating power?
Answer: Gamma rays
Explanation: Electromagnetic radiation emitted from the nucleus.
22. What is antimatter?
Answer: Matter composed of antiparticles.
Example: Positron (anti-electron)
23. What is a positron?
Answer: Antiparticle of electron
Explanation: Has positive charge.
24. What does a Geiger counter detect?
Answer: Radiation (alpha, beta, gamma)
25. What is atomic number?
Answer: Number of protons in the nucleus.
26. What is mass number?
Answer: Number of protons + neutrons.
27. What is a quark?
Answer: Basic building block of matter.
Explanation: Protons and neutrons are made of quarks.
28. Which quarks make up a proton?
Answer: Two up quarks + one down quark.
29. Which quarks make up a neutron?
Answer: One up quark + two down quarks.
30. What is the charge of a neutron?
Answer: Zero (neutral)
31. Which particles hold quarks together?
Answer: Gluons
Explanation: Carry the strong nuclear force.
32. What is the strong nuclear force?
Answer: Force that binds protons and neutrons in the nucleus.
33. What is the weak nuclear force responsible for?
Answer: Beta decay
Explanation: Responsible for radioactive decay.
34. What is half-life?
Answer: Time required for half the radioactive atoms to decay.
35. What is the unit of radioactivity?
Answer: Becquerel (Bq)
36. What is a chain reaction?
Answer: Self-sustaining fission process in nuclear reactors.
37. Which element is used in the hydrogen bomb?
Answer: Hydrogen isotopes (Deuterium, Tritium)
38. What is a neutrino?
Answer: Neutral subatomic particle with very small mass.
Explanation: Produced in nuclear reactions.
39. What is special relativity based on?
Answer: Constant speed of light + laws of physics same in all inertial frames.
40. What is general relativity based on?
Answer: Gravity = curvature of spacetime.
Explanation: Mass bends space.
41. What is spacetime?
Answer: Combination of three space dimensions + time.
42. What is time dilation?
Answer: Time slows down at high speed or strong gravity.
43. What is length contraction?
Answer: Moving objects appear shorter at near-light speeds.
44. Which device first confirmed Einstein’s relativity?
Answer: Michelson-Morley experiment.
45. What is a black hole?
Answer: Region where gravity is so strong that even light cannot escape.
46. What is a neutron star?
Answer: Extremely dense star made mostly of neutrons.
47. What is the atomic bomb based on?
Answer: Nuclear fission
Example: Uranium-235, Plutonium-239
48. What is the hydrogen bomb based on?
Answer: Nuclear fusion
Explanation: Much more powerful.
49. What is an isotope?
Answer: Atoms of the same element with different neutron numbers.
50. What is dark matter?
Answer: Invisible matter that does not emit light but affects gravity.
Explanation: 27% of the universe is dark matter.
⭐ Conclusion
Modern Physics GK—covering Quantum Mechanics, Relativity, and Nuclear Science—is essential for all competitive exams. These 50 questions help you master exam-focused concepts easily.