Video narration
Why does a rainbow appear only when sunlight and rain meet? Picture a sunny sky after a shower: sunlight travels through countless falling raindrops before it reaches you. Follow just one drop. As sunlight enters, it bends; this bending is called refraction. White sunlight already carries many colors, and the drop spreads them apart because each color bends a little differently. Next, the light reflects inside the drop, then bends again as it leaves, sending separated colors toward your eyes. That is the turn: the rainbow is not a colorful object sitting in the sky. It is sunlight redirected and separated by raindrops into the direction you happen to be looking. Different drops send the right colors from different parts of the sky, and together they form the curved band you see. So, why only when sunlight and rain meet? Because sunlight enters raindrops, reflects inside, then leaves split into colors for your eyes.