So, I was reading about the Casimir effect. Two mirrors facing each other attract to each other in a vacuum. The reason is due to pressure exerted on those mirrors from the multitude of EM waves (like light) outside of them, while in between those mirrors there are less waves present since long waves can't fit. The closer you bring those mirrors, the less waves are present and the stronger is the external pressure on them.
I always imagined waves as being made out of segments, like in the classic Nokia game Snake. I thought that the first segment of a wave to hit a reflective surface would be reflected first, while the last would be reflected last, and thus in between two mirrors the entire wave would simply fold. The first part hitting the first mirror would be reflected to the second mirror and hit it while the 5th part is only about to reach the first mirror.
Now I see I was wrong. Why?