Failure of Newton's corpuscular theory and success of photon theory of light Corpuscular theory of light States that:

Light is made up of small discrete particles called "corpuscles" (little particles) which travel in a straight line with a finite velocity.

According to Einstein,

Light is composed of small particle are known as photons. And energy of a photon is given by $E=h\nu$.

Corpuscular theory suggests particle nature of light. And existence of photons also suggests the particle nature of light. I see no difference between them. But why existence of photon is accepted but not corpuscles?
 A: The corpuscular theory was opposed to the wave theory, and was rejected when diffraction experiments confirmed the wave theory. The blackbody spectrum also confirmed the wave theory at low frequencies, but at high frequencies it didn't work. Thus, the photon theory emerged with its counterintuitive mix of particle and wave properties. The photon is not a corpuscle in the Newtonian sense. Subsequent experiments and refined models confirmed and extended the photon model. The counterintuitive wave/particle duality is a routine part of modern spectroscopy, with its gratings and photoelectric detectors.
A: As an example, when using the corpuscular theory refraction of light and Snell’s Law is predicted using Newtonian Mechanics but a requirement of the theory is that the speed of light in glass is greater than that in air which is found by experiment not to be true.  Theory related to photons have the speeds in different media which agree with experimental data and are based on Quantum Mechanics.
