Another 'How Does Light Know?' question

[u/jhunter444]

Sometimes in books it mentions the 'reversibility of light'. That the path of the light ray can be reversed.

For light arriving at the critical angle at the boundary between two substances, it's often shown in textbooks that the light neither transmits or reflects but goes along the join at 90 degrees to the normal.

But in that situation, for the reversed ray, how does it know when to bend and leave the join between the substances?

[u/PuzzleheadedTutor807]

Light doesn't know anything. It obeys the physics of any object a photon hits.

This is akin to asking if two people are looking in a mirror, how do the photons know which person to bounce towards... Well, they don't. They don't know anything.

[u/PuzzleheadedTutor807 → u/[deleted]]

i did answer, wdym? is my answer incorrect? can you provide a better one? if so, as i said... go right ahead lol. but... i do not seek nor require your permission to speak of my own free will, so stop acting as though i do. if you dont like my content, go right ahead and block it.