Explain these observations with numbers: (a) Why is red on the outside of the primary rainbow? (b) Why does the secondary bow look fainter and colour-reversed? (c) Why can't you see a rainbow at noon? Step 1: Primary bow: deviation D(λ) ≈ 138° total turning; the viewing angle from the antisolar point is 180° − 138° = 42°. Red (smaller n) deviates less, so red rays reaching your eye come from drops at slightly larger angle: red rim at ~42.5°, violet at ~40.6°. Red outside, violet inside. Step 2: Secondary bow involves two internal reflections: each reflection loses light (only partial TIR for some rays, plus absorption), so it is ~10× fainter. The extra bounce reverses the colour order: red now deviates least in the flipped geometry, appearing at ~50° (inner), violet at ~53° (outer). Step 3: At noon the Sun is high (say 70° elevation); the antisolar point is 70° below the horizon, and the 42° bow circle around it lies entirely underground. You need the Sun below 42° elevation — morning/evening — for the arc to clear the horizon.