Q.Explain experimentally observed facts of photoelectric effect with the help of Einstein's explanation.

Step 1. Since each absorbed photon liberates exactly one electron, increasing the intensity (more photons per second) increases the number of electrons emitted per second proportionally -- exactly matching the observed law that photocurrent is proportional to intensity.

Step 2. From $K_{max}=h\nu-\phi_0$, the maximum kinetic energy depends only on the frequency $\nu$ of the light, since intensity does not appear in the formula at all -- matching the observed independence of $K_{max}$ from intensity.

Step 3. Because a single photon must carry at least energy $\phi_0$ to free an electron at all, there is a minimum frequency $\nu_0=\phi_0/h$ below which no photon, however many arrive, has enough energy per photon to eject an electron -- matching the observed threshold-frequency law.

Step 4. Because the photon's entire energy is transferred to a single electron in one complete, instantaneous absorption event (not accumulated gradually as in the wave picture), there is no measurable time lag between illumination and electron ejection -- matching the observed instantaneous emission. …

Take each of the photoelectric effect's experimental facts in turn and show how Einstein's equa …

• Explaining only one or two of the four facts instead of covering intensity, frequency, …