Visible Light
Light, Sound and Waves

Hippo sun cream

Stories from Physics for 11-14 14-16 IOP RESOURCES

Hippopotamuses secrete a clear fluid that helps to control their body temperature. The fluid turns red-brown within a few minutes of release and gave rise to the myth that the creatures sweat blood. Researchers have found that the fluid blocks both UV and visible light of wavelengths 200-600 nm and so protects the animals from sunburn. The fluid contains red and orange pigments which researchers have labelled hipposudoric and norhipposudoric acid.

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