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J. Perelman
"Entertaining physics". Book 2.
Chapter 9. Reflection and refraction of light. Vision


Man is one of the few creatures whose eyes are adapted for simultaneous viewing of some of the subject: field of vision of the right eye just a little bit does not coincide with the field of vision of the left eye.

The majority of animals looking each eye separately. Visible their subjects do not differ with the relief to which we are accustomed, but their field of view is much more extensive than ours. Figure 1 shows a field of view of a man; each eye sees along the horizontal direction at an angle of 120°, and both angle almost cover each other (the eye is assumed to be stationary).

Figure 1. The field of vision of both eyes of the person.

Compare this drawing with Fig. 2, depicting the field of view of a hare; without turning his head, hare his wide-set eyes, he sees not only what is ahead, but that behind. Both fields of view, his eyes are closed and the front and back! Now you step back, why is it so hard to sneak up to the hare, not scaring him. But the hare, as it is clear from the drawing, absolutely can not see what is directly in front of his face; he has to see a very similar object, turn the head to one side.

Figure 2. The field of vision of both eyes of the rabbit.

Almost without exception, and hoofed ruminants possess such ability "comprehensive" view. Figure 3 shows the layout of the fields of view of the horse: they are behind not converge, but the animal just slightly turn your head to see things that are behind. Visualizations here, however, is not so clear, but from the animal pays the slightest movement made far range. Mobile predators, which usually have to be the aggressor, deprived of this ability to see around them; they have a "two-eyed" vision, but allowing to accurately estimate the distance to jump.

Figure 3. The field of vision of both eyes of the horse.

Entertaining physics J. Perelman


System Orphus


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