Title: InkPhysics / Quantum phenomena
On every note of this deck, unless a note says otherwise:
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Front: RECALL
Explain what happens in a collision offering less than the first excitation energy.
Back: The collision is elastic: the atom absorbs nothing and the electron keeps its kinetic energy.

Front: RECALL
State which transition gives the longest wavelength.
Back: The transition with the smallest energy gap, since λ = hc/ΔE.

Front: RECALL
State the relationship between threshold frequency and work function.
Back: The work function equals the photon energy at the threshold frequency: φ = hf₀.

Front: DEFINITION
Define: Ground state.
Back: The lowest energy level of an atom, in which its electrons normally sit.

Front: SPOT THE ERROR
Say what is wrong with this claim: Any collision can nudge an atom just a little.
Back: An atom cannot absorb just any amount of energy: its energy levels are discrete, so it accepts only the exact energy of a gap between levels; anything less leaves it unchanged.

Front: DEFINITION
Define: Work function.
Back: The minimum energy needed to release an electron from the surface of a metal.

Front: RECALL
Explain why energy levels are negative.
Back: Zero is set at ionisation, and a bound electron has less energy than a free one.

Front: DEFINITION
Define: Threshold frequency.
Back: The minimum frequency of incident radiation that will release electrons from a surface.

Front: RECALL
State the role of the phosphor coating in a fluorescent tube.
Back: It absorbs the ultraviolet photons emitted by de-exciting mercury atoms and re-emits the energy as visible light.

Front: RECALL
State the evidence that particles have wave properties.
Back: Electron diffraction: a beam of electrons passed through a thin crystal produces a pattern of rings.

Front: DEFINITION
Define: The electronvolt.
Back: The energy gained by an electron accelerated through a potential difference of one volt.

Front: RECALL
State the evidence that light has particle properties.
Back: The photoelectric effect: each emitted electron has absorbed a single photon.

Front: DEFINITION
Define: Stopping potential.
Back: The minimum potential difference that reduces the photoelectric current to zero: eV_s = E_k(max).

Front: RECALL
State the effect of greater intensity at fixed frequency.
Back: More photons arrive per second, so more electrons are emitted per second with the same maximum kinetic energy.

Front: SPOT THE ERROR
Say what is wrong with this claim: An atom can emit any colour it likes.
Back: An atom cannot emit any colour: each emitted photon's energy hf must equal the gap between two discrete energy levels, so only certain wavelengths appear, giving a line spectrum.

Front: RECALL
State the photon emission equation.
Back: hf = E_1 − E_2: the photon carries exactly the difference between the two levels.

Front: DEFINITION
Define: Photon.
Back: A discrete packet of electromagnetic energy: E = hf.

Front: RECALL
State the photoelectric equation.
Back: hf = φ + E_k(max): the photon energy pays the work function and the rest is the maximum kinetic energy.

Front: DEFINITION
Define: Ionisation energy.
Back: The minimum energy needed to remove an electron completely from an atom in its ground state.

Front: SPOT THE ERROR
Say what is wrong with this claim: Brighter light gives the electrons more energy.
Back: Brightness sets only how many photons arrive, not the energy of each. One electron absorbs one photon of energy E = hf, so below the threshold frequency no electrons escape however bright the light.

Front: RECALL
Explain why line spectra show that energy levels are discrete.
Back: Sharp lines mean only certain photon energies are emitted, and each equals a gap between two fixed levels.

Front: RECALL
State what the gradient of the maximum kinetic energy against frequency graph gives.
Back: The Planck constant h, the same for every metal.

Front: RECALL
State the condition for significant diffraction of a particle beam.
Back: The de Broglie wavelength must be comparable to the size of the gap or spacing.

Front: SPOT THE ERROR
Say what is wrong with this claim: Light is a wave, and electrons are particles.
Back: Neither label is complete: light also arrives as photons, and electrons also diffract. All matter and radiation show both wave and particle behaviour; the experiment decides which appears, with wavelength λ = h/p.

Front: RECALL
State the value of one electronvolt.
Back: 1 eV = 1.60 × 10^−19 J.

Front: DEFINITION
Define: Excitation.
Back: An atomic electron gaining exactly the energy needed to jump to a higher energy level.

Front: DEFINITION
Define: Ionisation.
Back: An electron gaining enough energy to leave the atom entirely, forming an ion.

Front: DEFINITION
Define: De Broglie wavelength.
Back: The wavelength associated with a moving particle: λ = h/p, where p is the particle's momentum.

Front: RECALL
State the effect of faster electrons on a diffraction pattern.
Back: Greater momentum means a shorter de Broglie wavelength, so the rings shrink towards the centre.