raytracing rendering moved to physics based rendering a while ago: the core idea is to approximate the physics of light as accurately as can reasonably be made fast. It's not like it's solving a wave equation directly, it's using a statistical sampling of a model of how light interacts with different interfaces between mediums. This is basically the easiest way to get photorealistic renders: the human brain is very good at noticing when your scene has non-physical lighting (not in a 'ahah, the specular highlights violate conservation of energy' way, but in a 'this looks fake' way).

(this approach was started by some researchers who basically said 'well, let's make a simple scene for real and measure everything and make our render look identical' https://en.wikipedia.org/wiki/Cornell_box )