OCR A Physics A-level: Nuclear and Particle Physics

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Questions and Answers

What is the term used to describe the difference in mass between the original nucleus and the resulting nucleus after a nuclear reaction?

Mass defect

What is the process by which two or more small nuclei combine to form a larger nucleus, releasing energy in the process?

Fusion

What is the reason for the decrease in binding energy per nucleon for high nucleon numbers?

Increased average distance between nucleons

What is the term used to describe the energy released when a large nucleus breaks apart into smaller daughter nuclei?

Fission energy Signup and view all the answers

What is the most stable isotope, according to the graph of binding energy per nucleon?

Iron-56 Signup and view all the answers

What is the term used to describe the attraction between nucleons in a nucleus?

Strong force Signup and view all the answers

What is the process by which a nucleus emits a high-energy particle or photon, resulting in a mass defect?

Radioactive decay Signup and view all the answers

What is the term used to describe the energy required to separate nucleons in a nucleus?

Work of separation Signup and view all the answers

What is the term used to describe the particle that is the antiparticle of a normal particle?

Antiparticle Signup and view all the answers

What is the characteristic of the gravitational force?

It is always attractive, has an infinite range, and acts on particles with mass. Signup and view all the answers

Which of the following is responsible for beta decay?

Weak nuclear force Signup and view all the answers

What is the relationship between mass and energy according to Einstein's hypothesis?

Mass is equivalent to energy, and the constant of proportionality is the speed of light squared. Signup and view all the answers

What is the range of the strong nuclear force?

Up to 3 fm, attractive, and below 0.5 fm, repulsive Signup and view all the answers

What is the result of the annihilation of matter and antimatter?

The release of a large amount of energy Signup and view all the answers

What is the role of the strong nuclear force in the nucleus?

It counteracts the repulsive electrostatic forces between protons in the nucleus Signup and view all the answers

What is the relationship between the energy change and the mass change according to Einstein's relation?

∆E = ∆m*c^2 Signup and view all the answers

What is the characteristic of the electromagnetic force?

It has an infinite range, acts on particles with charge, and can be attractive or repulsive. Signup and view all the answers

What is the interpretation of the concept of mass as a form of energy?

Mass can be thought of as energy in the form of mass-energy. Signup and view all the answers

What was the primary purpose of Rutherford's alpha-scattering experiment?

To test the Plum Pudding Model of the atom Signup and view all the answers

What was the expected outcome of Rutherford's alpha-scattering experiment?

That the alpha particles would be deflected by a large degree Signup and view all the answers

What was the actual outcome of Rutherford's alpha-scattering experiment?

That the alpha particles passed through the foil with little deflection Signup and view all the answers

What was the conclusion drawn by Rutherford from the experiment?

That the mass of the atom is concentrated at the nucleus Signup and view all the answers

What was the significance of the small proportion of alpha particles that were deflected by more than 90°?

It indicated that the charge on the nucleus was positive Signup and view all the answers

Why was a vacuum necessary in Rutherford's experiment?

To prevent the alpha particles from being stopped by air in the apparatus Signup and view all the answers

What was the role of the scintillators in Rutherford's experiment?

To detect the deflected alpha particles Signup and view all the answers

What was the thickness of the gold foil used in Rutherford's experiment?

Approximately 400 atoms thick Signup and view all the answers

What was the prevailing model of the atom before Rutherford's experiment?

The Plum Pudding Model Signup and view all the answers

What is a major assumption of radiocarbon dating?

The ratio of C-12 to C-14 has remained constant throughout history. Signup and view all the answers

Why is radiocarbon dating limited to samples younger than 5700 years?

The amount of C-14 becomes immeasurably small. Signup and view all the answers

What is the process by which small nuclei are fused together to produce larger nuclei and energy in stars?

Nuclear Fusion Signup and view all the answers

What is the purpose of the high temperatures and pressures in the star's core?

To overcome electrostatic repulsion between particles. Signup and view all the answers

What is the byproduct of the proton-proton chain in main sequence stars?

Deuterium nuclei and energy. Signup and view all the answers

What is the process by which the heaviest elements are synthesized?

Supernova Nucleosynthesis Signup and view all the answers

What is the advantage of artificial fusion reactors?

They have no radioactive by-products. Signup and view all the answers

Why is rubidium often used for dating old samples?

It has a longer half-life. Signup and view all the answers

What is the process by which carbon, nitrogen, and oxygen are synthesized in large stars?

CNO Cycle Signup and view all the answers

What is the main reason quarks have never been detected in isolation?

They are never alone in nature, only in combination with other quarks Signup and view all the answers

What is the consequence of the mass-energy equivalence in particle collisions?

Particles can be created or destroyed, with a transfer of kinetic energy and mass-energy Signup and view all the answers

What is the role of conservation rules in particle collisions?

They restrict the creation of particles with higher energy Signup and view all the answers

What is the consequence of the strangeness property in strong interactions?

It is conserved in strong interactions, unless the hadron decays via the weak force Signup and view all the answers

What is the main difference between quarks and leptons?

Quarks are affected by the strong force, while leptons are not Signup and view all the answers

What is the lepton number of an antilepton?

-1 Signup and view all the answers

What is the main reason neutrinos are difficult to detect?

They have a mass very close to zero and no charge Signup and view all the answers

What is the purpose of building higher energy particle colliders?

To discover higher energy particles and infer the existence of different quark flavors Signup and view all the answers

What is the consequence of the conservation of baryon and lepton number?

Particles with high energy cannot be created from lower energy collisions Signup and view all the answers

Study Notes

Rutherford's Alpha-Particle Scattering Experiment

Rutherford's experiment disproved the Plum Pudding Model of the atom.
Alpha particles were fired at a thin sheet of gold foil in a vacuum.
Most alpha particles passed through with only a slight deflection, indicating that the atom is mostly empty space.
A small proportion of particles were deflected by more than 90°, suggesting that the charge on the nucleus is positive.

Fundamental Forces

There are four fundamental forces in the universe: gravitational, electromagnetic, weak nuclear, and strong nuclear.
The gravitational force acts on particles with mass and is always attractive.
The electromagnetic force acts on particles with charge and has an infinite range.
The weak nuclear force is responsible for beta decay and acts on particles with specific properties.
The strong nuclear force acts between nucleons and quarks, counteracting the repulsive electrostatic force between protons in the nucleus.

Mass-Energy Equivalence

Einstein hypothesized that energy and mass are linked by the mass-energy equivalence.
The energy change is proportional to the mass change, with the speed of light squared as the constant of proportionality.
The concept of mass as a form of energy is demonstrated by the annihilation of matter and antimatter.
A mass defect occurs when a parent nucleus emits a daughter nucleus and a high-energy particle or photon, resulting in a mass difference between the total original mass and the total final mass of the products.

Nuclear Reactions

Fusion is the process of combining two smaller nuclei to form a larger nucleus, releasing energy in the process.
Fission is the process of breaking apart a larger nucleus into two smaller nuclei, releasing energy in the process.
The binding energy per nucleon is highest for iron-56, making it the most stable isotope.
For low nucleon numbers, the binding energy per nucleon increases as two small nuclei combine to form a larger nucleus.
For high nucleon numbers, the binding energy per nucleon decreases as a larger nucleus breaks apart into two smaller nuclei.

Antimatter

Every particle has a corresponding antiparticle.
Quarks have been deduced from particle collisions, and their existence has been inferred from conservation rules.
Leptons are fundamental particles not affected by the strong force, but subject to the weak nuclear force.
Examples of leptons include electrons, positrons, neutrinos, and muons.

Nuclear Fusion

Nuclear fusion occurs in stars, where small nuclei are fused together to produce larger nuclei and energy.
High temperatures and pressures are required to overcome the electrostatic repulsion between nuclei.
The proton-proton chain is the process by which fusion occurs in main sequence stars like the sun.
The CNO cycle is the predominant fusion process in larger stars.

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