In part 1 of QGD Optics, we examined how photons interacting with matter can create the diffraction patterns current physics associates with wave interference. It was shown that this behavior of light can be fully explained using the QGD purely corpuscular model of light.
- Photons are singularly corpuscular (so no wave-particle duality necessary)
- Photons are composite particles made of preons(+) therefore
- Photons have mass and that mass is equal to the number of preons(+) that form it
- Space is quantum-geometrical, that is, it has a discrete structure.
Hence, to predict the deflection of the trajectory of a photon, all we need to do is calculate the gravitational interaction between it and whatever matter it interacts with using the formula
Where 
Below are a few examples of the application of the formula to refraction of light. 
The image above illustrates the path of a single photon. The red circles represent positions of the photon. The green circles represent the radius of gravitational interaction significant enough to affect the trajectory of the photon. The regions highlighted in color represent the regions or parts of the lens the photons gravitationally interacts with. As we can see, the yellow regions are significantly smaller than the purple regions. The yellow regions contain less matter than the purple region, so the gravitational interaction between the photon with and the purple regions is greater than that with the yellow regions and results in a net interaction towards the purple region. The difference in volume, hence mass, of the regions evidently depends on the shape of the lens. The lens in this example is convex, which as we know will bend light towards a focal point.
The next image illustrates the path of a photon in a concave lens.
As one can see, the greater gravitational interaction is with the purple regions which will cause the photon to deviate outwardly from its path.
If in our examples 
or
If the value is positive, then the photon will be deviated toward the purple regions and 
As one can see from the given above and in part 1, QGD provides not only mathematical description of optical effects but a physical explanation. In the case of refraction, QGD optics show that the changes in trajectory of light passing through a lens depend on its geometry which in turn affect the shapes and volumes (hence masses) of the regions photons interact with.
In the above examples, we examined the refractions of a photon of arbitrary mass. But, as the equation indicates, the degree of refraction is also a function of the photon’s mass. Photons having different masses will be refracted differently. Everything else being equal, the more massive the photon, the greater the change in trajectory will be. This is why white light can be separated into photons of different colors. For example, since blue photons are deviated more than red or yellow photons, then red photons must be more massive than either red or yellow photons. And since photons in QGD are singularly corpuscular, this implies that photons of have different colors because they have different masses. Color depends on mass, not frequency.
In part 3 of this series of article we will discuss the reflection of light and the photoelectric effect and how the two are closely are related.
