суббота, 8 июня 2013 г.

How to see the fish

Have you ever tried to do a simple experiment: an ordinary magnifying glass is lowered into the water and try to treat it through submerged to the bottom of things? Be sure to try, and you will notice a rather surprising phenomenon: in the water magnifying glass next to nothing increases. And now dip into the water glass diminutive (biconcave) - and it turns out that it is also losing the largely their diminutive properties. Even stranger is the result of experience, if you have done it not with water, but with vegetable oil: it will turn out
just the opposite of what we are used to - lenticular glass will necessarily reduce all things, and dvoyakovygnutoe - increases it. Why would that be? If you remember the basic law of refraction of light better, all these wonders cease to amaze you with its surprise and strangeness. Lenticular lentils in air increases because the glass refracts light stronger than the air surrounding it. If we could make a lentil of the diamond, it would increase even more pronounced, because the refractive power of the diamond more than a glass. But the difference between the refractive properties of the glass and the water is relatively small, which is why, putting lentils in a glass jar with water, you will see that the light rays are refracted in the glass, do not have large deviation in its follow-up. That is why the water standard magnifying glass increases are much weaker than in the air, and the diminutive glass - much less reduce. And if you take the oil, it would appear that it refracts light rays are stronger than ordinary magnifying glass - hence the strange fact, at first glance, a phenomenon that in this fluid reduces the magnifying glass, and diminutives - increased. So, enough optical glass sink in the water, so that it has lost much of its optical properties. If we plunge into the water more than one glass, and a complex combination of glass, that is, a telescope, and there he would be completely unusable. And as our eyes - nothing more than an optical device, it is clear that in the water so the eye can not serve its purpose, as in the air. Now you understand that the vision of the fish must be some very special, and that there is much to ponder. In other words, the fact that the fish do not live in the air and in the water, that is, in an environment of strong air refracting light, this fact alone already creates for them a special optical phenomena, which we usually do not even suspect. More than just interesting to consider the question: how fish see us? And in general - in any form is our ground water creatures the world? An eminent American scholar of the last century - Robert Wood - at some point very seriously wondered studying this area. He built a very simple device which gives the opportunity to photograph objects in the form in which they must be drawn underwater creatures. The device is very simple, and it can make anyone. This ordinary camera without a lens, but filled with water, so that these rays before they reach the light-sensitive plate to pass through a water layer thickness of 10-15 cm. With this extremely simple device can be quite interesting pictures. For example, water can be removed from the circle of people standing near a small pond. Curious in this photo is that the fish from the bottom of the pond sees the whole person from head to toe, and not only the upper part of his torso. Earlier than you can approach the shore, the fish already sees you - interesting fact about which we usually do not suspect. The explanation for this apparent paradox lies in the law again, the refraction of light. If the pond was not filled with water and air, then from the bottom of the pool could be visible only those items that are in the space between the bottom and any point on the line extending from the bottom up at a tangent to the edge of the pond edge. Another thing, if the pond is filled with water - then the bottom of the fish can see objects that are somewhat lower than the seawater pond outside the water. The beam is refracted on the surface of the water near the edge, and thus the edge of the pond does not obstruct the fish items on the bank. In other words - the horizon of the fish much more than we used to think, and it is useful to remember all lovers of fishing. Another unexpected consequence of the law of refraction - a perversion of all forms of underwater objects and generally vnevodnyh for the inhabitants of the watery world. For example, straight lines of modern railway bridge over the river, the fish are drawn in the form of arcs. Dwell on the reasons for this optical phenomenon we will not - anyone familiar with physics, can he delved these reasons, the course of building a better world for the occasion. Remember, though, that we were flat bottom of a small pond seems to strongly concave due to refraction. For the same reason, and even a number of people who, for example, stand near the aquarium, the fish that inhabit it must seem quite differently - as if people are not a rank in a straight line, in fact, as an arc which is facing its convexity to the eye of fish. Something like this would be, among other things, upon reflection even rows in a convex mirror. Finally, we note another feature of underwater optics: fish and every at underwater creature always sees the light at the top of the circle itself, and absolutely no boundaries pond as you might think (except when the fish is very close to the shore). This again stems from the laws of refraction: constructing the path of rays and taking into account the existence of the so-called "critical angle" and the total internal reflection, you make sure that this should be so. And very interesting to note here that the closer the fish to the surface of the water, the less visible light circle above her head. And vice versa - with the immersion of fish in water deeper dimensions of this range increases considerably. These are some features of underwater optics, which many still do not even suspect, despite the fact that they can be on the basis of the laws of refraction of light, to anticipate in advance, and without any experiments. Work in this direction has been going for a long time. You can also talk about the theoretical interest, what these studies are for the many fans of science as expanding knowledge of ordinary people about the conditions of underwater life. And, of course, these studies are of great practical importance and - for diving view, scuba diving and even fishing. For example, any diver or a diver should be knowledgeable about all of the features of the underwater view, so as not to succumb to the worst possible moment any optical illusion misinterpreting distorted images of underwater objects, such an error can sometimes cost him his life. Similarly, the submarine captain should be the distinctive conditions of the underwater view in order to properly navigate. Finally, the fisher-hunter lying in wait for the fish and arranges for her network will operate more successfully, becoming, as it were, on the point of view of the persecuted.

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