Light is freely moving, unbound fotons.
Our eyes can see free fotons within a small range of frequencies (spin speeds). They correspond to the colours of the rainbow, and a little bit into UV. All free fotons, whether we can see them or not, interact with matter in the same way.
Interaction of fotons with surfaces
The surface of condensed matter made of atoms has an external negatively charged field that decreases in strength as it gets further from the surface. Below this is a thin relatively uniform negative field due to the protrusion of electron orbitals past the limit of positive nuclei. And there is below this a thin positive field due to the external layer of nuclei. The surface has a net neutral charge. Internally, condensed matter has a net neutral charge, with positive and negative locations due to electrons and nuclei.
The first thing that happens to a foton at the surface is refraction. It happens within the outer negative field that decreases in strength as it gets further from the surface. If a foton enters this negative charge gradient, its path is pulled toward the surface by a very simple mechanism. The orbits of the 2 fotinis in the photon are distorted by the surface field. The positini is attracted toward the surface, and the negatini repelled. As the positini is overall closer to the surface, the net force on the foton is attraction. The foton path curves toward the surface.
The above diagram shows the origin of the force required to bend light. Fotini orbits are elliptical and can be distorted. The electrical field distorts the orbits, bringing the positini path closer to the surface than the negatini path. Because the field has a gradient, the net force of attraction on the positini is greater than the repulsion of the negatini. The result is bending of the foton path toward the surface. The greater the distance between the fotinis, the smaller the net force of attraction that is created by that distortion. A field causes a particular amount of distortion of fotini paths. The greater the separation, the smaller this distortion is relative to the total orbit size. In this way, lower frequency light is refracted less than higher frequency light - because the foton's internal orbital separation is greater. Star lens effect The lens effect of stars is due to refraction, not gravity. The surface field of a star is like any other surface.
Diffraction is a special case of refraction - it is the same mechanism. Diffraction occurs when the negative surface field is relatively thin compared to the foton wavelength. This happens when the surface field is compressed by the presence of nearby surface fields. In this case, the foton interacts with a surface field that has a much stronger effect on the foton. This is because the change in field strength across the orbit of the foton is much greater, and the distortion of the fotini orbits is so much larger. In each wavelength, there is a 'nudge' of attraction from the part of the orbit where the positini is closer to the surface than the negatini. The part of the orbit where the negatini is closer is quite short and the repulsion force is relatively small. Each 'step' away from the center in the diffraction pattern corresponds to a 'nudge' from a single wavelength of the foton. The more steps in the pattern, the greater the number of wavelengths that have been nudged.
The path of the foton is deflected 0, 1 or more times, depending on how many wavelengths are influenced by the surface field.
After a foton is refracted in the negative field gradient, it then encounters the thin positive field below the refraction zone.
Reflection occurs when a foton bounces off this layer. It happens at the moment where the negatini is still within the strongest part of the negative refraction layer and the positini is just inside the thin positive layer. In this configuration, both fotinis experience strong repulsion simultaneously and they bounce off the surface.
The shallower the approach, the greater the probability that this geometry will occur. After this 'bounce' they experience exit refraction. So the apparent position of reflection above the surface is above the actual position of reflection. This is due to the optical distortion of refraction that occurs before and after reflection. It cannot be called an illusion because it is a product of the surface, not the mind.
The same mechanism is involved in internal reflection, the arrangement is geometrically reversed. The positini is in the lower side of the thin positive layer and the negatini is just inside the strongest part of the negative layer.
This model of reflection predicts a small amount of chromatic (color) aberration due to refraction at the surface affecting longer wavelengths less. It could be observed if amplified by many reflection events.
The above diagram shows how some fotons are reflected and some are not. The probability of reflection depends on the angle of approach, the foton separation and the surface field characteristics. Note the position of the positini and negatini required for reflection - so that both fotinis are repelled simultaneously.
The deeper the negative layer that is strong enough to repel a foton, the higher the probability that reflection will occur. Surfaces that we consider excellent reflectors have a negative layer with the strongest layer a similar distance from the positive layer as the foton separation in visible light. However, the negative field weakens as it approaches the positive layer, so smaller fotons are not reflected. A surface has a range of foton frequencies that it can reflect well. Visible light may or may not be included in these frequencies.