Each color bends differently

The colors start to split

The white light that bent into the water splits into colors. Violet light slows a little more than red light in water, so it bends a little more. The difference is tiny: in reality red and violet spread apart by only about 0.5°. The picture spreads them 8 times wider so you can see it.

Why?The color of light depends on how tightly packed its waves are. Red light has long gaps between its waves, and violet has short ones. Water slows light with shorter gaps a little more, so even when the colors enter at the same spot, each one bends by a different angle.

Learn moreThis splitting of colors because each bends differently is called dispersion. For water at 20 °C, the refractive index is 1.3305 for red light (wavelength 700 nanometers) and 1.3431 for violet light (wavelength 405 nanometers). We used the formula from the International Association for the Properties of Water and Steam (IAPWS).

Gap between red and violet in the water

0.45°

Refractive index · red

1.3305

Refractive index · violet

1.3431

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