Problem 3
Monochromatic light of frequency f illuminates a metal with work function W. In Einstein’s model, each electron absorbs one photon of energy hf; the maximum kinetic energy K_max of emitted electrons is measured, with material losses neglected. (a) Write energy conservation for an emitted electron. (b) Find K_max and threshold frequency f₀, and state the emission condition. (c) Give stopping potential V_s and explain how increasing intensity at fixed above-threshold frequency affects emission. Use SI units throughout and treat components as ideal exactly as specified. State sign conventions when writing equations and retain units in final results.
problems.proof.stepOf
problems.proof.analysis
The next part uses the preceding result as input rather than treating parts independently. This keeps conventions and physical state consistent throughout.
problems.proof.pitfall. Pitfall: do not change sign conventions between equations; a negative sign may encode direction rather than an invalid result.