How would Newton explain mirages? Suppose we think of light as photon packets with tiny momentum, then with this picture in mind, go and see the refraction of light in mirages:

We see that the packets of light photons must be continuously under a nature of force since it must change natural path direction. How would Newton have explained this force since he had no knowledge of wave theory?
 A: Newton literally wrote the book on Optics and knew perfectly well how to predict refraction.
He did posit a speculation on the reasons for refraction - that is, light was composed of tiny, very subtle pieces which were subject to kinematic laws and had the tendency to accelerate towards regions of higher density, an interaction in which they exchanged some of their extremely small momentum with the medium subject to the 2nd Law. This speculation is mostly false, although it bears a trivial resemblance to quantum mechanics. However, the light does exchange momentum with the medium as it curves, subject to a revised 2nd Law,
$\frac {d}{dt} \vec P = \frac {d}{dt} (E\vec v/c^2)$
Note how the right hand side simplifies to  Newton's $ m\vec a$ for $v \ll c$ and constant $m\gt0$.
A: This is not how photons are viewed. They are not moving particles in the Newtonian sense, and this has to do with the wave-particle duality of quantum theory. Light is absorbed by matter like a particle but propagates like a wave. Photons are the quanta of energy passed to matter. So refraction is an example of the wavelike nature of light, not the curved trajectories of light particles. It is interesting that Newton thought of light as literally particles, in the sense that you are implying here. But his conception differed greatly from the modern photon.
