Stories from Physics for 11-14 14-16
Levels of ultraviolet (UV) radiation can be high close to the North and South Poles. The effect occurs due to scattering resulting from the low position of the Sun in the sky and because snow and ice reflect as much as 80% of UV radiation. In snowy areas, high levels of UV radiation can lead to a kind of sunburn of the retina known as snow blindness. Most mammal eye lenses have therefore evolved to block UV radiation. However, it appears that reindeer may have developed some ability to detect UV radiation in the wavelength range of 300-320 nm for two important reasons: firstly, because a lichen they eat strongly absorbs UV and secondly, the fur of a key predator, the wolf, is highly reflective of UV radiation. Additionally, they may benefit from the variable reflection of UV from different kinds of snow.