Light act as Particle??

       After Hertz finished his significant experiment we can absolutely say that light is a kind of wave. But, when we observe the feature of light in a very small field, something strange happened! First, I should introduce one scientist, Max Planck, the pioneer of  quantum mechanics.

Max Planck

(https://zh.wikipedia.org/wiki/File:Max_Planck_1933.jpg)

      December 14(Quantum Day), 1900, Planck said to the whole world that energy shouldn't be continuous, there exist a basic amount of energy, called quantum. What did Planck meant? That means in the world, there's no energy equals half quantum, 4/3 quantum, it's like we can never pay with 1/2 NTD. Planck gave out a really crazy theorem and there's a crazy man who knew that how important quantum is to light

Albert Einstein

(https://zh.wikipedia.org/wiki/File:Einstein_1921_by_F_Schmutzer_-_restoration.jpg)

      A.D. 1905, Bern Switzerland, there's a civil servant worked in patent office, the man called "Albert Einstein.".He found out that if we regarded light with quantum, Photoelectric Effect can be easily solved. We can assume light is consisted with some quantum which Einstein called it "light quanta."(1926, G.N.Lewis changed the name to photon) With is rebellious theorem Einstein won the Nobel Prize in Physic in 1921.

    Isn't light a kind of wave?? Why Einstein say that we should assumed there exist photon, isn't this mean that light is particle? NO!! Einstein didn't said that light is particle but said that light act like particle in certain conditions. What a strange theorem???