I am able to understand how light can be modeled to have wave characteristics from Young's double slit experiment.
But I am unable to comprehend how we can understand light to have particle characteristics from the photoelectric experiment. How is it wave character not able to explain the phenomena observed in this experiment? And how is it that particle nature defeats the wave theory?
Best Answer
There have been attempts to describe the photoelectric effect by taking the EM field as a classical wave. For a discussion see a previous question "Can the photoelectric effect be explained without photons?". One of the answers describes that the photoelectric effect can be well explained considering the EM field more or less as a classical wave. To explain other experimental data though a quantized version of EM waves is needed.
On the second part of your question "And how is it that particle nature defeats the wave theory?" The above does not mean that these "wave quanta" (or photons) are particles in the sense of being localized objects flying around in space until they "hit" an atom kicking out an electron. A photon as a quantum of the waves is not localized or trackable as what one would think of a particle. Some physicists refere to these photons as particles which could lead to confusion (e.g. through which slit did they fly in these double slit experiments), but the bottom line is that even if you call these quanta particles they certainly do not defeat the quantum version of the wave theory.