Physics questions and solutions

Browse original practice and official past-paper questions. Each question has its own link, with its source and worked solution.

498 questions · Page 21 of 21

1. Q267 · Original practice · 1 mark
   A spacecraft passes station A and later station B. The two stations are at rest relative to each other and their clocks are synchronised in their own frame. A single spacecraft clock records both passages. Which interval is the proper time between these passage events?
   Special relativity
2. Q268 · Original practice · 3 marks
   An unstable particle has mean proper lifetime $1.80\,\mu\mathrm s$. A laboratory measures its mean lifetime as $3.00\,\mu\mathrm s$. The particle speed is constant. Use $c=3.00\times10^8\,\mathrm{m\,s^{-1}}$.
   Special relativity
3. Q269 · Original practice · 4 marks
   The axes show the spectral radiance per unit wavelength of a black body at $3000\,\mathrm K$. On these same axes, sketch the curve for the same source at $4500\,\mathrm K$. The curves are not separately normalised. Use $b=2.898\times10^{-3}\,\mathrm{m\,K}$.
   Quantum theory
4. Q270 · Original practice · 3 marks
   A student models a heated cavity using a classical model that lets each electromagnetic mode exchange energy continuously. It predicts an unbounded increase in emitted energy at very short wavelengths, unlike the observed finite spectrum.
   Quantum theory
5. Q271 · Original practice · 3 marks
   Rutherford extquotesingle s model places a small positive nucleus at the centre of the atom with electrons outside it. Consider an electron modelled as orbiting classically.
   Quantum theory
6. Q272 · Original practice · 4 marks
   Metals A and B have work functions $W_A=3.00\times10^{-19}\,\mathrm J$ and $W_B=4.00\times10^{-19}\,\mathrm J$. Use $h=6.626\times10^{-34}\,\mathrm{J\,s}$.
   Quantum theory
7. Q273 · Original practice · 1 mark
   An atom has three bound energies $-9.00$, $-5.00$ and $-2.00\,\mathrm{eV}$. An electron starts in the middle level. Ignore recoil, line broadening and multiphoton processes. Which photon can cause a transition to another bound level?
   Quantum theory
8. Q274 · Original practice · 5 marks
   In a photoelectric experiment the collector potential relative to the emitter at zero photocurrent is $V_c=-V_s$, where $V_s$ is the positive stopping-potential magnitude. A fitted graph of $V_s$ against frequency passes through $(6.00\times10^{14}\,\mathrm{Hz},0.500\,\mathrm V)$ and $(9.00\times10^{14}\,\mathrm{Hz},1.74\,\mathrm V)$. Use…
   Quantum theory
9. Q275 · Original practice · 3 marks
   A gas initially has its electrons in the ground state. Its absorption spectrum has narrow lines at $310\,\mathrm{nm}$ and $620\,\mathrm{nm}$. Candidate model X has levels $0$, $2.00$ and $4.00\,\mathrm{eV}$; model Y has levels $0$, $3.00$ and $4.00\,\mathrm{eV}$. Assume only these levels and neglect recoil. Use $hc=1240\,\mathrm{eV\,nm}$.
   Quantum theory
10. Q276 · Original practice · 3 marks
    Hydrogen emits photons when electrons end at $n_f=2$. Use $R=1.097\times10^7\,\mathrm{m^{-1}}$.
    Quantum theory
11. Q277 · Original practice · 4 marks
    The diagram shows an idealised atom with three bound levels $-8.00$, $-5.00$ and $-1.00\,\mathrm{eV}$. An electron absorbs a photon from the ground state to the top level, then returns through the middle level in two emission steps. Use $hc=1240\,\mathrm{eV\,nm}$.
    Quantum theory
12. Q278 · Original practice · 3 marks
    An electron in an allowed Bohr orbit satisfies $n\lambda=2\pi r$ and $p=h/\lambda$. Treat its momentum as nonrelativistic.
    Quantum theory
13. Q279 · Original practice · 1 mark
    Which statement correctly compares a proton with an electron in the Standard Model?
    The Standard Model
14. Q280 · Original practice · 2 marks
    A display lists quarks as up, down, charm and strange, and lists leptons as electron, electron neutrino, muon and muon neutrino. It lists particles rather than antiparticles.
    The Standard Model
15. Q281 · Original practice · 1 mark
    A system contains three antiquarks, one electron and one electron antineutrino. What are its total baryon number B and total lepton number L?
    The Standard Model
16. Q282 · Original practice · 4 marks
    The partial particle-interaction diagram shows an incoming and outgoing electron on the left and an incoming and outgoing positron on the right. Time increases upward. This is the exchange/scattering channel, not annihilation.
    The Standard Model
17. Q283 · Original practice · 4 marks
    In a neutron, a down quark changes into an up quark by emitting a $W^-$ boson. The boson produces an electron and an electron antineutrino. Up and down charges are $+2e/3$ and $-e/3$.
    The Standard Model
18. Q284 · Original practice · 7 marks
    Light illuminates a metal of work function $W=2.00\times10^{-19}\,\mathrm J$. The most energetic emitted electrons enter a uniform $1.00\times10^{-3}\,\mathrm T$ magnetic field perpendicular to their velocity and follow circular paths of radius $2.00\times10^{-3}\,\mathrm m$. Assume single-photon emission and nonrelativistic electrons. Use…
    Quantum theory