屈折
くっせつ · kussetsu · JLPT N1 · noun
refraction
🌈 屈 bend + 折 fold: a bend or dent, and light bending (refraction)
屈 means bend and 折 means fold, so the word covers a physical bend or dent and also light bending as it passes from air into water or glass.
折 — hand 扌 + axe 斤
Originally written as 折 with a hand (扌) breaking or chopping something with an axe (斤), depicting the act of snapping or cutting in two. The core meaning 'to break, snap, fold' extends metaphorically to 'bend,' 'turn back,' and 'discount' (as in reducing a price by breaking off part).