Particles, Radiation, and Quantum Phenomena

Vocabulary practice flashcards covering fundamental particles, interactions, decay processes, electromagnetic radiation, and quantum phenomena based on A-Level physics lecture notes.

Nucleons

Protons and neutrons located in the nucleus at the centre of an atom.

Specific Charge

The charge-mass ratio of a particle, calculated by dividing its charge by its mass, measured in $\text{C}\,\text{kg}^{-1}$.

Proton Number ($Z$)

The number of protons in the nucleus of an atom.

Nucleon Number ($A$)

The total number of protons and neutrons in the nucleus of an atom.

Isotopes

Atoms with the same number of protons but different numbers of neutrons.

Carbon Dating

A technique used to find the approximate age of organic material by calculating the remaining percentage of carbon-14 using its starting value and known half-life.

Strong Nuclear Force (SNF)

The force that keeps nuclei stable by counteracting electrostatic repulsion between protons; it is attractive up to separations of $3\,\text{fm}$ and repulsive below $0.5\,\text{fm}$.

Alpha Decay

Decay occurring in large nuclei with excess protons and neutrons, which causes the proton number to decrease by $2$ and the nucleon number to decrease by $4$.

Beta-Minus ($\beta^-$) Decay

Decay occurring in neutron-rich nuclei where a neutron decays into a proton, emitting an electron and an electron antineutrino; proton number increases by $1$ and nucleon number remains unchanged.

Neutrino

A fundamental neutral particle with zero charge and negligible mass, hypothesised and later observed to account for the conservation of energy in beta decay.

Antiparticle

A counterpart to every particle that shares the exact same rest energy and mass, but possesses opposite values for all other properties such as charge.

Positron ($e^+$)

The antiparticle of the electron, with a mass of $9.11 \times 10^{-31}\,\text{kg}$, rest energy of $0.511\,\text{MeV}$, and a charge of $+1.6 \times 10^{-19}\,\text{C}$.

Photon

A packet of electromagnetic radiation that transfers energy without mass, having an energy directly proportional to its frequency ($E = hf$).

Annihilation

The process occurring when a particle and its corresponding antiparticle collide, converting their masses and kinetic energy into two photons moving in opposite directions to conserve momentum.

PET Scanner

A medical imaging device that creates 3D images of the body by detecting gamma photons released when positrons from an introduced radioisotope annihilate with electrons in the patient.

Pair Production

The conversion of a single photon into an equal amount of matter and antimatter, which can only happen if the photon's energy exceeds the combined rest energy of both particles.

Exchange Particles

Particles that mediate fundamental forces between interacting particles by transferring energy and momentum.

Electron Capture

A weak interaction where a nuclear proton interacts with an orbital inner-shell electron, resulting in a neutron and an electron neutrino ($p + e^- \rightarrow n + \nu_e$).

Leptons

Fundamental particles that cannot be broken down any further and do not experience the strong nuclear force.

Hadrons

Particles composed of quarks that experience the strong nuclear force, categorized into baryons, antibaryons, and mesons.

Baryons

Hadrons made of $3$ quarks, characterized by a baryon number of $+1$.

Mesons

Hadrons formed from a quark and an antiquark, having a baryon number of $0$.

Muon

A lepton often referred to as a "heavy electron" that decays into an electron.

Strange Particles

Particles produced via the strong nuclear interaction in pairs but decaying via the weak interaction, such as kaons.

Strangeness

A quantum property that must be conserved in strong interactions, but can change by $0$, $+1$, or $-1$ during weak interactions.

Quarks

Fundamental particles that make up hadrons, existing in flavours such as up ($u$), down ($d$), and strange ($s$).

Photoelectric Effect

The emission of photoelectrons from the surface of a metal when light above a threshold frequency is shone upon it.

Threshold Frequency

The minimum frequency of incident light required to cause the emission of photoelectrons from the surface of a given metal.

Work Function ($\phi$)

The minimum energy required for electrons to be liberated from the surface of a metal.

Stopping Potential ($V_s$)

The potential difference required to stop the fastest-moving photoelectrons, fulfilling the relationship $E_{k(\text{max})} = e V_s$.

Excitation

The transition of an atomic electron to a higher discrete energy level after absorbing energy from an incoming photon or colliding free electron.

Ionisation

The complete removal of an electron from an atom occurring when the absorbed energy exceeds the atom's ionisation energy.

Ground State

The lowest, original energy level that an electron occupies within an atom.

Electron Volt ($\text{eV}$)

The energy gained by one electron when passing through a potential difference of $1\,\text{V}$, equal to $1.6 \times 10^{-19}\,\text{J}$.

Line Spectrum

A spectrum consisting of discrete wavelengths emitted by de-exciting electrons, proving that atomic electrons occupy discrete energy levels.

Line Absorption Spectrum

A continuous spectrum containing black lines at specific wavelengths caused by cool gas atoms absorbing photons equal to exact differences between discrete energy levels.

Wave-Particle Duality

The principle stating that matter and electromagnetic radiation exhibit both wave-like characteristics (e.g., diffraction) and particle-like characteristics (e.g., photoelectric effect).

De Broglie Wavelength

The wavelength associated with a particle having mass and velocity, defined by $\lambda = \frac{h}{mv}$.