ConceptModern Physics
← All conceptsPhotoelectric effect & photons
photon energy E=hf=hc/λ, Einstein equation Ekmax=hf-W (work function/threshold frequency), instantaneous emission independent of intensity below threshold, two-wavelength work-function comparisons
11 ways this goes wrong. Each one is a named misconception the questions are built to catch.
- All photon energy becomes KESets the photoelectron's kinetic energy equal to the full photon energy hf, ignoring the work function spent escaping the metal.→
- E proportional to wavelengthUses photon energy proportional to wavelength rather than to frequency (E=hf=hc/λ).→
- Emission below threshold over timeThinks low-frequency light eventually frees electrons if shone long enough, ignoring the threshold frequency.→
- Intensity equals frequencyConflates light intensity with frequency, treating brighter light as automatically higher-frequency.→
- Intensity raises max KEExpects increasing light intensity to raise the maximum kinetic energy of photoelectrons.→
- Max KE proportional to frequencyTreats Ekmax as directly proportional to frequency, ignoring the subtracted work-function term so a doubled frequency doubles the KE.→
- Photon energy vs intensity confusedBelieves brighter (more intense) light gives each electron more energy, rather than more electrons.→
- Stopping voltage depends on intensityBelieves the stopping potential changes with light intensity rather than with frequency.→
- Two-wavelength work-function errorWhen comparing two illuminating wavelengths on the same metal, treats the work function as changing with wavelength rather than being a fixed property of the metal.→
- Wave theory explains photoeffectMaintains that classical wave theory accounts for the instant, threshold-dependent emission.→
- Work function sign wrongAdds the work function in Einstein's equation (KE=hf+W) instead of subtracting it.→
