Why do opals show rainbow colors?
Show answer & explanation
Answer: Silica spheres diffract light
Trapped water refracts light — Wrong. Opals contain ~10% water between silica spheres, but colors come from light diffraction by the ordered sphere structure, not water refraction.
Chemical impurities create colors — Wrong. Unlike colored gemstones (ruby has chromium), opal's color is structural, not chemical. It's from light interacting with silica sphere arrangement.
Silica spheres diffract light ✓ — Correct! Opals are made of tiny silica spheres (150-300 nanometers) arranged in orderly grids. Light waves diffract (bend) around these spheres, creating interference patterns that separate light into rainbow colors—like soap bubbles! Different sphere sizes and arrangements create different color plays. It's physics, not chemistry!
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