Questions and Answers
What is the purpose of carbon-14 dating?
Stable nuclei are those that have an optimal number of protons and neutrons, preventing decay.
True
What role does the strong nuclear force play in the stability of nuclei?
It counteracts the electrostatic force of repulsion between protons.
During alpha decay, the proton number decreases by __, and the nucleon number decreases by __.
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Match the types of nuclear decay with their descriptions:
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What happens to the nucleon number during beta-minus decay?
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Unstable nuclei will always undergo alpha decay.
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What observation led scientists to understand that energy was not conserved during beta-minus decay?
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What is the mass of an electron?
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Annihilation involves a particle and its corresponding antiparticle colliding to produce one photon.
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What is the primary application of annihilation in medicine?
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What is required for pair production to occur?
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The antiparticle of an electron is called the ______.
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Exchange particles carry energy and momentum between particles experiencing the same fundamental force.
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Match the following particles with their properties:
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What is the Planck constant value used in the energy of photons equation?
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Name the four fundamental forces in nature.
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Photons have mass.
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In particle physics, pair production involves the conversion of a photon into matter and ________.
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Match the fundamental forces with their respective exchange particles:
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What is the relationship between the energy of photons and the frequency of electromagnetic radiation?
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What are the constituents of an atom?
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Electrons have a positive charge.
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What is the proton number denoted by, and what does it represent?
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A neutron has ______ charge.
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Match the following particles with their properties:
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What is the specific charge of a proton?
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Isotopes have different numbers of protons.
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What does the nucleon number (A) represent?
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What describes the minimum energy required for electrons to be emitted from the surface of a metal?
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If the frequency of light is above the threshold frequency, no photoelectrons will be emitted even with increased intensity.
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What is the equation that relates energy, work function, and maximum kinetic energy of photoelectrons?
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The potential difference needed to stop photoelectrons is called the ______.
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Match the following terms with their definitions:
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What happens to an electron when it gains enough energy from a free electron?
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In a fluorescent tube, the excitation of electrons results in the production of light.
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What occurs when an electron falls back to its ground state after excitation?
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Study Notes
Constituents of the Atom
- An atom consists of protons, neutrons, and electrons.
- The nucleus contains protons and neutrons (nucleons), while electrons orbit it in shells.
- Particle properties can be defined in SI and relative units, including charge, mass, and specific charge.
Charge and Mass of Particles
- Proton: +1.6 × 10⁻¹⁹ C, mass 1.67 × 10⁻²⁷ kg, specific charge 9.58 × 10⁷ Ckg⁻¹.
- Neutron: Neutral charge, mass 1.67 × 10⁻²⁷ kg, specific charge 0.
- Electron: -1.6 × 10⁻¹⁹ C, mass 9.11 × 10⁻³¹ kg, specific charge 1.76 × 10¹¹ Ckg⁻¹.
Atomic Number and Isotopes
- Proton number (Z) represents the number of protons; nucleon number (A) is the count of protons and neutrons.
- Isotopes are atoms with identical proton numbers but differing neutron counts (e.g., carbon-14).
- Carbon dating utilizes the decay of carbon-14 to estimate the age of organic materials.
Stable and Unstable Nuclei
- The strong nuclear force (SNF) stabilizes nuclei by overcoming proton repulsion.
- SNF is short-range, attractive up to 3 fm, but repulsive below 0.5 fm.
- Unstable nuclei decay to achieve stability when they have too many protons or neutrons.
Types of Decay
- Alpha decay occurs in large nuclei with excess protons and neutrons, reducing proton number by 2 and nucleon number by 4.
- Beta-minus decay affects neutron-rich nuclei, increasing proton count by 1 while nucleon count remains unchanged.
- Neutrinos were theorized due to energy conservation issues observed during beta decay.
Particles and Antiparticles
- Each particle has a corresponding antiparticle with opposing properties—e.g., positron is the antiparticle of the electron.
- Photon properties: energy measured in MeV, travels as massless packets.
Annihilation and Pair Production
- Annihilation occurs when a particle meets its antiparticle, converting their mass into energy, generating two photons.
- PET scanners use annihilation to produce detectable gamma photons for medical imaging.
- Pair production converts a high-energy photon into a particle and antiparticle pair if the photon energy exceeds their total rest energy.
Fundamental Forces and Particle Interactions
- Four fundamental forces: gravity, electromagnetic, weak nuclear, strong nuclear.
- Exchange particles transfer energy and momentum between particles, influencing their interactions.
- In electromagnetic interactions, photons are absorbed by electrons; higher frequency light increases photoelectron emission.
Photoelectric Effect
- Work function (ϕ) is the minimum energy to release electrons from a metal surface.
- The stopping potential (Vs) is the voltage needed to halt photoelectrons with maximum kinetic energy.
- The photoelectric equation relates work function, maximum kinetic energy, and light frequency: E = hf = Φ + Ek(max).
Electron Collisions and Energy Levels
- Electrons exist in discrete energy levels and can transition between them through excitation or ionization.
- Excitation occurs when an electron gains energy; ionization happens if energy exceeds the ionization energy.
- Fluorescent tubes use excitation to generate light by returning electrons to their ground state, releasing energy as photons.
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Description
This quiz covers the key concepts of particles in physics, specifically focusing on the constituents of atoms, including protons, neutrons, and electrons. Understand the structure of the atom, the roles of nucleons, and the properties of these fundamental particles. Perfect for students preparing for the AQA A-level exam.
