Every entry height

Different heights, different angles

Sunlight does not hit just one spot on a raindrop. It lands evenly all over, from the middle to the edge. Light that enters at a different height takes a different path inside and leaves at a different angle. Use the slider below to change the entry height.

Why?Light that enters right in the middle (height 0) hardly bends, reflects off the back wall and heads back toward the Sun (0°). Moving toward the edge, the exit angle grows until it peaks at about 42° around height 0.86. Light entering even closer to the edge leaves at smaller angles again.

Learn moreEntry height is measured from the middle of the drop, with the drop’s radius counted as 1. Move the slider slowly and watch the angle at the top: near 42° there is a stretch where the angle barely changes even as the height changes. That is the key to the next scene.

Exit angle

42°

Height with the largest angle

0.86

Largest exit angle

42°

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