←All concepts
Concept · Modern Physics
Atomic structure & spectra
Rutherford gold-foil/α-scattering (small dense nucleus, refutes plum-pudding), Bohr energy levels, photon emission/absorption Ephoton=Ehigh-Elow, number of spectral lines from level n = n(n-1)/2
Switches you to Physics
Named traps
11 ways this goes wrong.
Each is a named misconception the questions are built to catch. Open one for the move that tempts, and the fix.
- Bigger jump, lower frequencyAssociates a larger energy-level transition with a lower-frequency photon, reversing E=hf.→
- Emission/absorption swappedHas the atom absorb a photon when dropping to a lower level (or emit when rising), reversing the transition.→
- Energy levels continuousTreats atomic energy levels as a continuous range rather than discrete quantized states.→
- Level energy sign ignoredIgnores the negative sign of bound-state energies, mishandling which transition is larger.→
- Model attribution swappedCredits the wrong scientist or experiment for a model (e.g. Bohr for the gold-foil scattering, or Thomson for quantized energy levels).→
- Most alphas deflected stronglyClaims a large fraction of α particles bounced back in the gold-foil experiment, rather than the rare large-angle scattering that revealed a tiny dense nucleus.→
- Orbiting electron radiates continuouslyBelieves a Bohr-orbit electron continuously emits radiation, contradicting stable stationary states.→
- Photon energy as level valueSets the photon energy equal to a single level's energy rather than the difference between two levels.→
- Scattering supports plum-puddingReads the gold-foil results as confirming the plum-pudding model instead of refuting it in favor of a concentrated nucleus.→
- Spectral line positions differExpects emission and absorption lines of the same element at different wavelengths.→
- Spectral-line count uses nCounts the number of possible spectral lines from level n as n (or n-1) instead of n(n-1)/2 distinct transitions.→
Key formulas
No formula sheet is matched to this concept yet. Work it from first principles, and watch the traps.
Shaky underneath?
If the concept underneath still feels loose, patch it here before coming back to CSCA questions.
FoundationsPhysics 2 breadthMechanics foundationsAdvanced mechanics support