When my mother and I were returning home from my grandfather and grandmother by car late at night, I saw two glowing lights in the distance. I was scared at first, but when we got closer, I saw that it was a cat!

I was wondering why her eyes glow so brightly, because human eyes don’t glow in the dark? I began to look for an answer to this question. I asked my mother, grandfather, woman, looked in books, I found a lot of interesting things on the Internet.

My grandfather, Omelyanenko Yuri Aleksandrovich, is a doctor, and he told me about the structure and functions of the human eye, showed me a picture, explained how we perceive light.

The reflected light first hits the transparent cornea of ​​the eye, passes through the anterior chamber filled with liquid, and the hole in the iris - the pupil. Having passed through the lens - the lens, which can change its curvature, and the vitreous body, the light enters the retina of the eye and a reduced mirror-spherical image of the object in question appears on the surface. The human eye, it turns out, is very similar in structure to a photographic camera. It contains almost all the elements: the lens - the lens, the retina - the photosensitive layer of photographic film where the image of the object is formed.

The human eye is so complex! But let's get back to cats.

It turns out that cats' glow-in-the-dark eyes have done a lot of damage to their reputation. For centuries, black cats were generally considered companions of witches, and the belief that cats' eyes glow themselves has survived to this day. However, simple experience convinces us otherwise. If you put a cat in a room without windows, then in complete darkness its eyes will not glow.

The shine of a cat's eyes is explained simply - they reflect the light that enters them. The secret of the glow of the eye is in its structure.

The cat has big and beautiful eyes. Their pupil opens much larger than a human's. Thanks to such a pupil, the maximum possible amount of light enters the retina. The RETINA is a layer of light-sensitive cells at the back of the eye. The back wall of the eyeball is concave, and in front of it there is a collecting lens - the lens, then it turns out something like a spotlight. When a ray of light reaches the light-sensitive retina through the cornea and lens, it is not completely absorbed. Part of the light reaches the inner vascular reflective membrane, the so-called tapetum. This is a layer of silvery crystals. The tapetum reflects light, forcing it to pass through the retina again, as if back, that is, the light is used twice. It is reflected and a glow appears on the surface of the eye. So, if you stand directly in front of the animal, you can see quite a strong glare, even if the eyes reflect only a faint reflection of the night sky, the light of approaching headlights. The surrounding darkness makes this shine even more noticeable. This arrangement of the eye significantly increases its sensitivity. For example, cats are able to clearly see surrounding objects in light levels that are six times less than what we need. The tapetum can have different colors - bluish, greenish, yellowish. The tapetum does not necessarily cover the entire fundus. It can be located only on part of the retina, in the shape of a crescent, triangle or diamond. In such cases, one can observe a curious effect related to the fact that the tapetum gives a strong blue-green reflection, and the fundus of the eye without tapetum gives a weaker, red reflection. Sometimes you get pictures in which two eyes of the same animal glow different colors, or even two colors are visible in one eye.

This is why cats' eyes glow in the dark! Now I want to find out how owl vision works and why it sees better in the dark than in light.

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