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
\text{At fixed f>f_0, increasing intensity raises photon flux, not K_max}
problems.proof.analysisInsert the intermediate result into the relevant definition or equation to obtain the final expression. Checking signs and limits catches a wrong branch or omitted constraint.