Why do rainbows form semicircles?
Show answer & explanation
Answer: Light refracts at specific angle
Rain falls in arc patterns — Wrong. Rain falls straight down. Rainbow's arc comes from refraction angle—light bends 40-42° inside raindrops, creating circular arc centered opposite sun.
Light refracts at specific angle ✓ — Correct! Rainbows form at specific angle: light enters raindrop, refracts (bends), reflects internally, refracts again exiting—total deviation ~42° (red) to 40° (violet). All raindrops at this angle from antisolar point contribute to rainbow—forms cone/circle with your eye at apex. Ground blocks lower half—you see semicircle. From airplane, you see full circle! Double rainbows have secondary reflection (50-53°, reversed colors)!
Gravity bends light downward — Wrong. Gravity doesn't bend visible light significantly (only in extreme cases like black holes). Rainbow arc comes from refraction geometry—42° angle.