Nuclear reaction, explained answer
1. What is a nuclear reaction?
- A process where nuclei change by collision or decay, releasing or absorbing energy.
2. In a nuclear reaction, which quantities are always conserved?
- Mass number, atomic number, energy, and momentum.
3. What is nuclear fission?
- Splitting of a heavy nucleus into lighter nuclei with energy release.
4. What is nuclear fusion?
- Combining light nuclei into a heavier nucleus releasing energy.
5. Which particles often initiate nuclear fission chain reactions?
- Slow (thermal) neutrons.
6. What is a product of fission of Uranium-235?
- Two lighter nuclei, neutrons, and energy.
7. What type of reaction powers the sun?
- Nuclear fusion of hydrogen nuclei.
8. What is a critical mass?
- Minimum mass needed to sustain a chain reaction.
9. What happens when a nucleus absorbs a neutron and emits gamma radiation without fission?
- Radiative capture.
10. Which type of nuclear reaction releases more energy per event?
- Fusion generally releases more energy per reaction than fission.
11. What is the role of moderators in nuclear reactors?
- Slow down neutrons to sustain fission.
12. What particles are emitted during beta decay?
- Electrons or positrons and neutrinos.
13. What does the Q-value of a nuclear reaction represent?
- Net energy released or absorbed during the reaction.
14. In endothermic reactions, Q-value is:
- Negative, energy is absorbed.
15. Which nuclear process is used in nuclear power plants to generate electricity?
- Controlled nuclear fission.
16. What happens if a chain reaction becomes uncontrolled?
- It leads to an explosion or a bomb.
17. What is spontaneous fission?
- Fission that occurs without neutron bombardment.
18. What is an example of a nuclear reaction used in medicine?
- Radioisotope production via neutron activation.
19. In a nuclear reaction, if the product nuclei have less mass than reactants:
- The difference in mass converts to energy.
20. Which reaction releases neutrinos?
- Beta decay emits neutrinos or antineutrinos.
21. What is neutron capture in nuclear reactions?
- When a nucleus absorbs a neutron without fission, often followed by gamma emission.
22. What is meant by cross-section in nuclear physics?
- A measure of the probability of a nuclear reaction occurring, in units of area.
23. What are slow neutrons called?
- Thermal neutrons, with lower kinetic energy suitable for fission.
24. What particles are released in beta-plus decay?
- Positron and neutrino are emitted when a proton changes into a neutron.
25. In terms of conservation, what changes in beta decay?
- A neutron converts to a proton or vice versa, conserving atomic number and mass number.
26. What is transmutation?
- Changing one element into another by nuclear reactions.
27. What is an exothermic nuclear reaction?
- A reaction that releases net energy (Q-value positive).
28. Which term defines the minimum neutron energy needed for fission?
- Threshold energy.
29. What particles are involved in artificial radioactivity?
- Bombarding nuclei with neutrons or charged particles to induce radioactivity.
30. What is a radioactive tracer?
- Radioisotope used to follow chemical or biological processes.
31. What is the role of control rods in a nuclear reactor?
- Absorb excess neutrons to regulate the fission chain reaction.
32. What is the meaning of "breeder reactor"?
- Reactor that produces more fissile material than it consumes.
33. What is the main fuel in breeder reactors?
- Uranium-238 or Thorium-232, converted to fissile isotopes.
34. What is an alpha particle composed of?
- Two protons and two neutrons.
35. What is the penetrating ability of beta particles?
- Moderate; they can penetrate skin but stopped by metal sheets.
36. Which device detects ionizing radiation by cloud trails?
- Cloud chamber.
37. What is the significance of the Q-value in fusion reactions?
- The energy released, which must overcome Coulomb barrier.
38. What is neutron moderation?
- The process of slowing down fast neutrons to thermal energies.
39. Which particles cannot be deflected by magnetic fields?
- Neutrons, since they have no charge.
40. What does binding energy per nucleon indicate?
- Nuclear stability; higher values mean more stable nuclei.
