Light is pure energy, it is a massless ray of energy that travels at the constant speed of light through space. The wave particle duality of light comes about from light behaving like a particle when it is detected. Newton was the first to propose such a theory when he talked of corpuscles:
From Google search by way of Wikipedia Of Newton’s Corpuscular Theory of Light (this predates Heisenberg’s Physical Principles of the Quantum Theory):
Isaac Newton argued that the geometric nature of reflection and refraction of light could only be explained if light was made of particles, referred to as corpuscles, because waves do not tend to travel in straight lines. Newton sought to disprove Christiaan Huygens' theory that light was made of waves.
So when light is detected it becomes quantised into discrete corpuscles known as photons. Each photon is the harmonic excitation of the wave, that is the full wavelength of the fundamental frequency, so both the positive and negative excitation curves on an oscilloscope. I feel this quantisation is related to Einstein’s Photo-electric Effect, for which he won an Nobel Prize, which states that light rays incident on a Caesium crystal get absorbed and electrons are emitted, but when the light gets brighter or more intense the electrons emitted do not increase proportionally because only the light of a certain wavelength, fundamental frequency, will excite an electron from the caesium whereas other light rays would not have enough energy to pass the interaction threshold and get an electron out for the photon. We see the same thing in photoelectric solar cells, they need to be made up of several layers of semiconductors which would each absorb a slightly different spectrum of light and convert it to electrons.
My theory is that light is pure energy, just a ray and massless, but the interaction of light with a detector can produce a very strong interaction with the light source. The light ray is travelling through space-time at the speed of light, the group velocity of the light ray is the constant c the speed of light, but the phase velocity of the light ray, which also transmits information can be different, faster than the speed of light, and can also travel backwards along the length of the light ray to its source. As the light ray travels through space it revolves around its axis propagating as waves do, in the ocean and other places, and the ridges where the wave is in the same orientation along its path can be moving at a different speed and direction to the actual light ray itself, like if you walked down the up escalator.
The point is that light is a ray until it gets detected which is a process that turns it into a particle through the detection apparatus, which is like processing a signal on an analogue to digital signal convertor, ADC, after it is detected and amplified. So it seems to have a momentum even though it is massless, I think it is related to Einstein’s relativity theory, but is more to do with the secondary and tertiary products of a light ray detection which produces the effect of the light ray appearing to have momentum that can move. In my idea I think that you can strengthen the interaction between the light source and detector by having a stronger detection and thus would create an effect similar to momentum as the light would affect the relationship between the source and detector but would just be carrying energy or information. The detection would then alter the state of the system in some way which would then produce a change that would make the light ray appear to have a momentum and act like a particle, but in fact that is not the case. It is like signalling a warning to another human and an action being taken to change the course of a ship. We cannot say that the light ray is responsible for it but the ship avoided the rocks because the pilot saw the light.