光線
こうせん · kousen · JLPT N2 · noun
radio beam
💡 光 (light) + 線 (line) = a line of light, a ray or beam
光 means light and 線 means line or thread, so 光線 is a line of light travelling from one point to another.
光 — fire 火 (top) + person 儿 (bottom)
Originally a pictograph of a person with fire above their head, depicting a torchbearer or the radiance from a flame. The character evolved to mean 'light' or 'brightness' in general, and by extension 'glory' and 'to shine.' The modern top component is a stylized form of 火 (fire).