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MOST IMPORTANT SCIENTIFIC DISCOVERIES
Spectrum of light. History and essence of scientific discovery
Directory / The most important scientific discoveries Descartes as early as 1629 he found out the course of rays in a prism and in glasses of various shapes. He even invented mechanisms for glass polishing. Scottish professor Gregory built a model of a telescope remarkable for its time, based on the theory of concave mirrors. Thus, even then, practical optics had reached a significant degree of perfection and was one of the sciences that most occupied the then scientific world. By 1666 when Newton began optical research, the theory of refraction has advanced very little since the time of Descartes. There were very confused theories and concepts about the colors of the rainbow and the colors of bodies: almost all scientists of that time limited themselves to the statement that this or that color represents either a "mixing of light with darkness" or a combination of other colors. It goes without saying that such an obvious fact as iridescent coloration, observed when objects are viewed through a prism or through poor optical glass, was only too well known to everyone involved in optics. But everyone was firmly convinced that all kinds of rays, when passing through a prism or through a magnifying glass, are refracted in exactly the same way. Coloring and iridescent borders were attributed solely to the roughness of the surface of the prism or glass. At first, Newton worked hard on polishing magnifying glasses and mirrors. These works introduced him empirically to the basic laws of reflection and refraction, with which he was already theoretically familiar from the treatises of Descartes and James Gregory. Newton begins a series of experiments, which later the great scientist himself described in detail in his writings. "At the beginning of 1666, that is, when I was busy grinding non-spherical optical glasses, I took out a triangular glass prism and decided to use it to test the famous phenomenon of colors. To this end, I darkened my room and made a small hole in the shutters in order to so that a thin ray of sunlight can pass through it. I placed a prism at the entrance of the light so that it could be refracted to the opposite wall. At first, the sight of the bright and vibrant colors resulting from this amused me. But after a while, forcing myself look at them more closely, I was surprised by their elongated shape, in accordance with the known laws of refraction, I would expect them to be round.On the sides, the colors were limited to straight lines, and at the ends, the fading of light was so gradual that it was difficult to determine exactly what their shape; it even seemed to be semi-circular. Comparing the length of this color spectrum with its width, I found that it is about five times larger. The disproportion was so unusual that it aroused in me more than the usual curiosity, the desire to find out what could be its cause. It is unlikely that the different thickness of the glass or the border between light and darkness could cause such a light effect. And I decided at first to study precisely these circumstances and tried what would happen if light was passed through glasses of different thicknesses, or through holes of different sizes, or when a prism was installed outdoors, so that the light could be refracted before it was narrowed by the hole. . But I have found that none of these circumstances is significant. The pattern of colors in all cases was the same. Then I thought: could some glass imperfections or other unforeseen accidents be the reason for the expansion of colors? To test this, I took another prism, similar to the first, and placed it in such a way that the light, passing through both prisms, could be refracted in opposite ways, with the second prism returning the light to the direction from which the first deflected it. And thus, I thought, the ordinary effects of the first prism would be destroyed by the other, while the unusual ones would be enhanced by the multiple refractions. It turned out, however, that the beam scattered into an elongated shape by the first prism was brought round by the second prism as clearly as if it had not passed through anything at all. Thus, whatever the cause of the elongation, it is not due to random irregularities. I next moved on to a more practical consideration of what might produce the difference in the angle of incidence of rays coming from different parts of the sun. And from experience and calculations, it became obvious to me that the difference in the angles of incidence of the rays coming from different parts of the Sun cannot cause, after their intersection, a divergence by an angle noticeably larger than the one at which they previously converged, but the value of this angle is not more than 31 32 minutes; therefore, another reason must be found that could explain the appearance of an angle of two degrees forty-nine minutes. Then I began to suspect whether the rays, after passing them through the prism, were curvilinear, and whether, in accordance with their greater or lesser curvilinearity, they did not tend to different parts of the wall. My suspicion was heightened when I remembered that I had often seen a tennis ball which, when struck obliquely with a racket, described a similar curved line. For the ball is informed in this case both circular and translational motion. That side of the ball where the two motions agree must push and push the adjacent air with more force than the other side, and will therefore excite proportionately more air resistance and reaction. And for this very reason, if the rays of light were spherical bodies (Descartes' hypothesis) and when they move obliquely from one medium to another, they would acquire a circular motion, they would have to experience greater resistance from the ether washing them from all sides from that side. , where the movements are consistent, and would gradually bend to the other side. However, despite all the plausibility of this assumption, I did not observe any curvature of the rays when checking it. And besides (which was sufficient for my purpose), I observed that the difference between the length of the image and the diameter of the hole through which the light passed was proportional to the distance between them. Gradually eliminating these suspicions, I came at last to the experimentum crucis, which was as follows: I took two boards and placed one of them directly behind the prism of the window, so that the light could follow through a small hole made in it for this purpose and fall on the other. board, which I placed at a distance of about 12 feet, and a hole was also made in it so that some of the light could pass through it. I then placed another prism behind this second board in such a way that the light, having passed through both these boards, could follow through the prism, being refracted in it again before it hit the wall. Having done so, I took the first prism in my hand and slowly turned it back and forth, approximately around the axis, so that different parts of the image falling on the second board could successively pass through the hole in it, and I could observe where the wall was thrown rays second prism. And I saw, by changing these places, that the light tending to that end of the image, to which the greatest refraction took place by the first prism, experienced in the second prism a much greater refraction than the light directed to the other end. And thus the true reason for the length of this image was discovered, which cannot be other than the fact that the light consists of rays of different refraction, which, regardless of the difference in their occurrence, fall on different parts of the wall in accordance with their degrees of refraction ... " Various unfounded "suspicions" - as Newton called his hypotheses - finally led him to the idea of making the following experiment. Just as at the beginning of his analysis he isolated a thin beam of white rays from the sun, so now the idea came to his mind to isolate a part of the refracted rays. This was the second and most important step in spectrum analysis. Noticing that in his experience the violet part of the spectrum was always at the top, blue below, and so on down to the bottom red, Newton tried to isolate the rays of one color and study them separately. Taking a board with a very small hole, Newton applied it to the surface of the prism that faces the screen, and, pressing it against the prism, moved it up and down, and without difficulty achieved the seclusion of single-color, for example, only red, rays that passed through a small hole in a board. A new, even thinner beam of pure red rays was subject to further investigation. Passing red rays through the second prism. Newton saw that they were refracted again, but this time everything was almost the same. Newton even thought that it was exactly the same, that is, he considered one-color rays to be completely homogeneous. Having repeated the experiment on yellow, violet and all other rays, he finally understood the main feature that distinguishes one or another of the rays from rays of another color. Passing through the same prism now only red rays, now only violet rays, and so on, he finally became convinced that white light consists of rays of different refraction and that the degree of refraction is closely related to the quality of the rays, namely to their color. It turned out that red rays are the least refracted and so on up to the most refracted - violet. Newton formulated the conclusions of the largest discovery as follows: "1. Just as rays of light differ in their degree of refraction, so they also differ in their tendency to exhibit one particular color or another. Colors are not qualities of light resulting from refractions or reflections in natural bodies (as usually considered), but the essence is natural and innate qualities, different in different rays ... 2. The same degree of refraction always corresponds to the same color, and the same color always corresponds to the same degree of refraction. And the connection between colors and refraction is very precise and clear: the rays either agree exactly in both respects, or they do not agree proportionally in them. 3. The patterns of color and the degree of deviation inherent in each particular kind of rays are not changed either by refraction or reflection from natural bodies, or by any other cause that I could observe. “Newton's theories made possible the development of physics as an exact science,” Vladimir Kartsev writes in his book. “It began to approach mathematics more and more and move further and further away from philosophy. It was before publication to be approbated in the Royal Society, to be heard and discussed there.This happened on February 8, 1672 ... ... It was Newton's first scientific article. The unusual resonance that such a small work received, its enormous influence on the fate of Newton and the fate of science as a whole, force our contemporaries to pay more attention to the new that it brought to the world of scientific research. This article marks the advent of a new science - the science of the new time, a science free from groundless hypotheses, based only on firmly established experimental facts and on logical reasoning closely related to them. Now, at the end of the XNUMXth century, it is difficult to appreciate the sensationalism and unusualness of this little article by Newton. But the deepest minds of the seventeenth century quickly discerned in a small letter "crazy ideas", leading in the end to an explosion of established and habitual ideas, which, in turn, only recently triumphed over Aristotelian metaphysics. The discovery of different refraction of rays served as the starting point for a number of scientific discoveries. The further development of Newton's idea has led in recent times to the discovery of the so-called spectral analysis. Author: Samin D.K.
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