Scales sardines, herring and sprat violates the laws of optics

Scales European sardines, herring and sprat appeared arranged in such a way that violates the laws of classical optics and allows these fish reach a maximum reflectance and become invisible to predators from all angles.

The study's authors are interested in fish scales after notice that they reflect light, almost polarizing it, regardless of the angle of incidence and reflection. This behavior is very unusual in terms of the classical optics - the larger the angle of incidence, the stronger must be polarized light.

It turned out that the scales of sardines, herring and sprat consists of two types of crystals with strictly specified optical properties. According to the scientists, the two types of crystals consist of two biominerals - guanine and hypoxanthine. The combination of these substances makes them special optical medium where the light beam is split into two separate components, in violation of the classical law of refraction of light.

As the scientists explain, such structures are known in physics as the birefringent crystals. The trajectory of the light beam when driving through such objects depends on its polarization - non-polarized light will pass through it freely, and polarized waves will be refracted in a special way.

The combination of the two types of crystals with different refractive index makes the fish in almost perfect "mirror", which does not produce polarized light beams. Roberts and his colleagues believe that this optical "armor" to prevent glare and sunbeams when light is reflected from the body of the fish, which it can detect birds of prey and other inhabitants of the sea.

via factroom.ru