A different drop for each color

Red on top, violet below

Each raindrop sends out every color, but only one of them reaches your eye. From a drop 42.4° from the shadow point, red reaches you. From a slightly lower drop at 40.6°, violet does. That is why a rainbow is red on the outside (top) and violet on the inside (bottom). The colors you see each come from a different set of raindrops.

Why?Red bunches up at the largest angle (about 42.4°) and violet at the smallest (about 40.6°). To catch red at its larger angle, you have to look at drops farther from the shadow point, which means higher in the sky.

Learn moreThe person next to you sees their own rainbow, made by light from different drops. As you walk, your rainbow moves with you to keep the same angle, so you can never reach it. The drops keep falling, but new drops fill their place, so the rainbow stays put.

Angle between red and violet

1.8°

Drops that send red

42.4° from the shadow point

Drops that send violet

40.6° from the shadow point

calculated from the refractive index of water (IAPWS, 20 °C) and the laws of refraction and reflection