7. Nuclear Physics

Question 1

What is the basic structure of an atom according to the particle model?

Answer 1

An atom consists of a small central nucleus composed of protons and neutrons, surrounded by electrons.

Question 2

What provides evidence of the distribution of mass in the atom?

Answer 2

The scattering of alpha particles by thin metal foil provides evidence of the distribution of mass in the atom.

Question 3

What are the relative masses and electric charges of protons, neutrons, and electrons?

Answer 3

Proton: Relative mass = 1, Relative charge = +1
Neutron: Relative mass = 1, Relative charge = 0
Electron: Very small mass, Relative charge = -1

Question 4

What is an isotope?

Answer 4

Isotopes are atoms of the same element that have the same number of protons but a different number of neutrons.

Question 5

What is the process by which unstable nuclei emit particles or radiation to become more stable?

Answer 5

The process is called radioactive decay.

Question 6

What are the types of particles emitted during radioactive decay?

Answer 6

Unstable nuclei emit alpha particles, beta particles, or neutrons, and electromagnetic radiation as gamma waves.

Question 7

What is background radiation, and where does it come from?

Answer 7

Background radiation is the radiation around us all the time, originating from sources such as radioactive substances in the environment, cosmic rays, or medical devices like X-ray machines.

Question 8

What is a half-life in the context of radioactive decay?

Answer 8

The half-life of a radioactive isotope is the time it takes for the number of nuclei of the isotope in a sample to halve, or the time it takes for the count rate from a sample containing the isotope to fall to half its initial level.

Question 9

What is the composition of an alpha particle, and what is its role in nuclear decay?

Answer 9

An alpha particle consists of two neutrons and two protons, essentially a helium nucleus. In nuclear decay, unstable nuclei emit alpha particles, reducing their mass and atomic number.

Question 10

What is the primary difference between alpha, beta, and gamma radiation?

Answer 10

Alpha radiation consists of helium nuclei (two protons and two neutrons), beta radiation is high-speed electrons, and gamma radiation is electromagnetic radiation.

Question 11

What is meant by the term “nuclear fusion”?

Answer 11

Nuclear fusion is the process by which two light nuclei combine to form a heavier nucleus, releasing a large amount of energy in the process.

Question 12

What are the conditions required for nuclear fusion to occur?

Answer 12

Nuclear fusion requires extremely high temperatures and pressures to overcome the repulsion between positively charged nuclei, allowing them to fuse.

Question 13

How does nuclear fusion differ from nuclear fission in terms of energy release?

Answer 13

In nuclear fusion, energy is released when light nuclei combine to form heavier ones, whereas in nuclear fission, energy is released when a large, unstable nucleus splits into smaller ones.

Question 14

What is the primary source of energy generation in stars?

Answer 14

Nuclear fusion is the primary source of energy generation in stars, where hydrogen nuclei combine to form helium nuclei, releasing energy in the process.

Question 15

Explain the role of control rods in a nuclear reactor.

Answer 15

Control rods in a nuclear reactor absorb excess neutrons to control the rate of fission and prevent a runaway chain reaction.

Question 16

What is radioactive contamination, and what hazard does it pose?

Answer 16

Radioactive contamination refers to the unwanted presence of radioactive atoms on other materials. The hazard arises from the decay of these contaminating atoms, which emit ionizing radiation, posing health risks to living organisms.

Question 17

What is irradiation, and how does it differ from contamination?

Answer 17

Irradiation is the process of exposing an object to ionizing radiation. Unlike contamination, where radioactive atoms adhere to other materials, irradiation does not make the object itself radioactive. However, precautions must still be taken to protect against the hazards of the radioactive source used in irradiation.

Question 18

What is significant about the range of half-life values of radioactive isotopes?

Answer 18

Radioactive isotopes exhibit a wide range of half-life values. The most unstable nuclei have short half-lives, leading to rapid decay with the emission of a large amount of radiation in a short time. Conversely, the least unstable nuclei have long half-lives, emitting radiation at a slower rate over an extended period.

Question 19

How do the uses and dangers of radioactive isotopes vary based on their half-life values?

Answer 19

Radioactive isotopes with short half-lives are often used in applications requiring rapid decay, such as medical imaging and certain industrial processes. However, they pose immediate hazards due to their intense radiation emission. Isotopes with long half-lives find applications in fields like radiometric dating but can also present long-term health and environmental risks due to prolonged radiation exposure.

Question 20

What is nuclear fission?

Answer 20

Nuclear fission is the process of splitting a large and unstable nucleus, resulting in the release of energy.

Question 21

What are the two fissionable substances commonly used in nuclear reactors?

Answer 21

The two fissionable substances commonly used in nuclear reactors are uranium-235 and plutonium-239. It’s noteworthy that the majority of nuclear reactors primarily utilize uranium-235.

Question 22

Describe the process of nuclear fission.

Answer 22

In nuclear fission, a uranium-235 or plutonium-239 nucleus absorbs a neutron, becoming unstable. This unstable nucleus then splits into two smaller nuclei, releasing two or three neutrons and a significant amount of energy. This energy release is much greater than that from a chemical reaction involving a similar mass of material.

Question 23

What is a chain reaction in the context of nuclear fission?

Answer 23

A chain reaction occurs when neutrons from the fission of one nucleus go on to cause further fission in neighboring nuclei. In a nuclear reactor, control rods are used to absorb fission neutrons, ensuring that, on average, only one neutron per fission leads to additional fission and energy transfer.

Question 24

What are the implications of nuclear reactions in terms of waste production?

Answer 24

Nuclear reactions produce radioactive waste, which can remain hazardous for a long time depending on its half-life and decay products. The disposal of such waste requires careful management due to its radioactive nature, which may influence the decision to use nuclear power for electricity generation.

Question 25

What conditions are necessary for nuclear fusion to occur?

Answer 25

For nuclear fusion to occur, the force of repulsion between the two positive nuclei must be overcome. This typically happens at very high temperatures and pressures.