Consider a stone embedded in the sand on the sea shore which is being hit repeatedly by the water waves from the sea. As the wave represents continuous flow of mechanical energy, the energy imparted to the stone goes on increasing as long as the wave continues to hit it. As soon as the stone acquires sufficient energy required to uproot it, it will be uprooted.
An alternative method to uproot the stone could be to hit it hard with another stone. The second stone transfers its kinetic energy to the embedded stone in an instant (rather than over a period of time ...
The expert explains why the existence of a cutoff frequency in the photoelectric effect more strongly favors a particle theory rather than a wave theory of light. A detailed explanation is provided.