by proving it
Einstein's photoelectric effect work found that the incident light involved in the photoelectric effect was made of individual quanta (photons) that interacted with the metal's electrons like discrete particles, not waves.
When Einstein discovered photoelectric effect!
1921
Albert Einstein
Albert Einstein
einstein
Albert Einstein
albert einstein
he pooped in a cup
Apex Light is made of photons.
Apex Light is made of photons.
The photoelectric effect proves that light is composed of quanta called photons (packets of enegy) and therefore proves the Photon Theory composed by Einstein.