Cue Column | Notes Column
| Cue / Question | Notes |
|---|---|
| What is the photoelectric effect? | Emission of electrons from a metal surface when light of frequency ≥ ν_{0} strikes it. First observed by Hertz (1887). |
| Einstein's photoelectric equation | KE_max = hν − φ = h(ν − ν_{0}). Units: [ML^{2}$$T^{-2}] = J or eV |
| What is stopping potential ? | Retarding potential that stops the most energetic photoelectrons: e = KE_max → = (hν − φ)/e |
| What does depend on? | Frequency ONLY. NOT intensity. Intensity changes photocurrent (number of electrons), not . |
| What is the threshold frequency ν_{0}? | Minimum frequency for emission: ν_{0} = φ/h. Below ν_{0}, no emission regardless of intensity. |
| What is work function φ? | Minimum energy to eject an electron from the surface. φ = hν_{0}. Unit: eV or J. |
| Photon energy and momentum | E = hν = hc/λ [ML^{2}$$T^{-2}]; p = h/λ = E/c [M]; rest mass = 0; speed = c always |
| de Broglie hypothesis | Every moving particle has wavelength λ = h/(mv) = h/p. [L] = m |
| Electron through potential V | λ = h/√(2meV) = 1.227/√V nm (electrons ONLY) |
| Mass dependence of λ | At same v or same V: λ ∝ 1/√m. Heavier particle → shorter wavelength. |
| Davisson-Germer experiment | Electron diffraction from Ni crystal (1927) confirmed de Broglie's hypothesis. |
| KE_max vs ν graph features | Straight line; slope = h (same for ALL metals); x-intercept = ν_{0}; y-intercept = −φ |
| vs ν graph features | Straight line; slope = h/e (same for ALL metals); x-intercept = ν_{0} |
| Photocurrent vs V features | Sigmoid curve; different intensities → different saturation currents but SAME |
Summary
The dual nature of radiation and matter unifies wave and particle descriptions. Light acts as a particle (photon) in the photoelectric effect — Einstein's equation KE_max = hν − φ explains all observations. The stopping potential depends only on frequency, not intensity. Matter exhibits wave nature via de Broglie's hypothesis λ = h/p; confirmed by the Davisson-Germer electron diffraction experiment. The KE vs ν and vs ν graphs both have universal slopes (h and h/e respectively) independent of metal type. For NEET: master the three graphs, the electron-through-potential shortcut λ = 1.227/√V nm, and mass-ratio comparisons.