A-Level Physics · Topic 8
Quantum physics and nuclear physics: every key term you need (+ practice quiz)
16 flashcard terms for A-Level Physics Topic 8, written to match the course framework. Study them here, then drill them as interactive flashcards, or test yourself with the 8-question quiz — free, no account needed.
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Photoelectric effect Electrons are emitted only above a threshold frequency, whatever the intensity. Evidence that light behaves as discrete photons.
Work function The minimum energy needed to release an electron from a metal surface. Determines the threshold frequency.
Photon energy The Planck constant times frequency. Explains why intensity alone cannot free an electron below the threshold.
Stopping potential The reverse voltage just preventing any photoelectrons reaching the collector. It measures their maximum kinetic energy.
Wave-particle duality Matter and radiation both show wave and particle behaviour. Which appears depends on the experiment performed.
De Broglie wavelength The Planck constant divided by momentum. Electron diffraction confirms that particles have an associated wavelength.
Energy level A discrete allowed electron energy in an atom. Transitions between levels emit or absorb photons of definite energy.
Emission vs absorption spectrum Emission shows bright lines from downward transitions; absorption shows dark lines where those photons were removed from a continuous spectrum.
Electronvolt The energy gained by one electron accelerated through one volt — about 1.6 times ten to the minus nineteen joules.
Rutherford scattering Most alpha particles passed straight through gold foil while a few rebounded, showing the atom is mostly empty with a tiny dense nucleus.
Binding energy The energy needed to separate a nucleus into its nucleons, equivalent to the mass defect through mass-energy equivalence.
Binding energy per nucleon Peaks near iron-56. Fusion of light nuclei and fission of heavy nuclei both move towards this peak, releasing energy.
Radioactive decay constant The probability per unit time that a given nucleus decays. Related to half-life by the natural logarithm of two.
Half-life The time for half the undecayed nuclei to decay. Constant for an isotope and unaffected by temperature or chemical state.
Alpha, beta and gamma penetration Alpha is stopped by paper, beta by a few millimetres of aluminium, gamma only attenuated by thick lead or concrete.
Nuclear fission moderation A moderator slows fast neutrons so they are far more likely to induce further fission, sustaining the chain reaction.
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