Q.Explain why photoelectric effect cannot be explained on the basis of wave nature of light.

Step 1. According to wave theory, the energy in light is spread continuously and uniformly over the wavefront, so a more intense beam should deliver more energy to each electron and free it with a greater kinetic energy. But experiment shows $K_{max}$ does not depend on intensity at all -- only on frequency.

Step 2. Wave theory places no restriction on frequency: given enough intensity, electrons should eventually be freed at any frequency. But experiment shows emission simply does not happen below a definite threshold frequency, however intense the light.

Step 3. Since wave theory spreads the incoming energy thinly across many electrons over the wavefront, each individual electron should take a long time (calculated at hours to days for realistic intensities) to slowly accumulate enough energy to escape. But experiment shows emission is essentially instantaneous (well under a nanosecond). …

Walk through wave theory's three specific, contradicted predictions: intensity-dependent K_max, no thresh …

• Giving only one of the three failures instead of all three. …