>>13785382the term photon was coined to explain the photoelectric effect. the photoelectric effect is when light of a frequency above a particular threshold causes an electron to be ejected from the material.
this lead Einstein to claim that light acts as a particle with energy proportional to frequency, multiplied by a fitting constant.
The real solution is however is that matter is a discrete ensemble of quantum bodies and light is a wave. when light interacts with matter(absorption or emission) it does so in discrete packets.
Young proved with his double slit experiment a very long time ago that light is a wave since it interferes with itself.
