IB›IB Physics HL›Mind mapsE.2 Quantum physicsIB Physics HL: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsPhotoelectric effectBelow threshold frequency: no emission at allAbove it, emission is instantaneousMax EkE_kEk depends on frequency, not intensityHigher intensity: more photoelectrons per secondEvidence for particle nature of lightEinsteinPhoton energy E=hfE = hfE=hf, one photon to one electronEmax=hf−ΦE_{max} = hf - \PhiEmax=hf−ΦWork function: minimum energy to free electronAt threshold: Φ=hf0\Phi = hf_0Φ=hf0EmaxE_{max}Emax against f: gradient is hMatter wavesde Broglie: λ=hp\lambda = \frac{h}{p}λ=phAccelerated through V: p=2mEkp = \sqrt{2mE_k}p=2mEkSame EkE_kEk: heavier particle, shorter λEveryday objects: λ about 10⁻³⁴ mQuantum physicsphotons and matter waveshfhfhfΦ\PhiΦλ\lambdaλDualityElectrons diffract through thin graphiteRings show wave nature of matterHigher voltage: shorter λ, smaller ringsDiffraction needs λ comparable to spacingComptonScattered X-rays have longer wavelengthPhoton momentum is hλ\frac{h}{\lambda}λhΔλ=hmec(1−cosθ)\Delta\lambda = \frac{h}{m_ec}(1 - \cos\theta)Δλ=mech(1−cosθ)Largest shift at 180°: about 4.85 pmExam tipsBrighter light gives more, not faster, electrons1 eV=1.60×10−19 J1\,\text{eV} = 1.60 \times 10^{-19}\,\text{J}1eV=1.60×10−19J: convertΔλ same for any incident wavelength