change of direction light beam
Alternative descriptionsIn astronomy, this is the apparent deviation of stars from their true position in the sky
In biology, a deviation from the normal structure of an organism, often expressed only in a different size or color
Change in the apparent position of the star caused by the finite value of the speed of light and the movement of the observer along with the Earth
One of the key features of mirrors is focus, the definition of which varies depending on the type of mirror in question. In the case of a concave mirror, the fire is the point where the beam of parallel rays, after reflection, tends to converge: it is located in front of the mirror.
In the case of a convex mirror, the fire is the point where a beam of parallel rays, after reflection, appears to diverge: it is located behind the mirror. From the previous statements it is concluded that fire does not exist in the case flat mirror: A ray of parallel rays will be reflected by maintaining parallelism and therefore the rays do not tend to converge or deviate from a single point.
Distortion, defect, degrades the image in optical instruments
Deviation from the norm
Deflection of light rays under the influence of the speed of the Earth's movement
Distortion in optical systems
Image distortion in optical systems
Apparent deviation of the luminary from its true position
Deviation from something, as well as distortion of something
Let's continue to calculate the focal length, that is, the distance between the mirror and the focus. This depends on the curvature of the mirror: the more the mirror becomes "flat", the more the fire moves away, to the extreme case of a nearly flat mirror with infinite focal length. This establishes a direct proportionality relationship between radius and focal length as it determines curvature.
We will now consider the case of a concave mirror. Running the application, we see how the various rays that make up part of the beam converge at approximately the same point; this is especially true for radii closer to the optical axis. Note also that for radii closest to the optical axis, the focal length is almost equal to half the radius.
Apparent displacement heavenly bodies, caused by the rotation of the Earth around the Sun and its rotation around its axis
Distortion caused by optical instruments
Misconception
J. lat. physical friability and scattering broken rays Sveta; astronomer. a visible change in the position of the luminary, from wasting time on reaching us with a ray of light and from the earth running around the sun; break, slope
Let us consider what was said earlier, that fire increasingly moves away from the bend and that with an almost specular mirror the fire tends to infinity: we can consider the fire of a flat mirror to be the Sun, for if it is true that the reflection made by it preserves the parallelism of the rays, they must necessarily return to their origin when they appear in the mirror. In this case the fire coincides with any ray, so we may state that it tends to be constant when the radius of the sphere from which the mirror is made is very large; By adding that, as stated earlier, the fire usually lies halfway through the radius, we can set the focal length.
Newton also admitted that light could have weight. It is now generally accepted that light falling on any object exerts pressure on it. This is equivalent to saying that light has mass. Naturally, the corresponding values are quite small. In Eddington's book "Space, Time, Gravity"
it is said that the mass of sunlight falling on the Earth every twenty-four hours is about 160 tons. But if light has mass, then, regardless of whether it obeys Newton’s or Einstein’s laws, a light ray passing near the Sun must, like planets or comets, move along a curved path. The fact that light "travels" much faster than any planet or comet naturally means that the deflection of light near the Sun will be much weaker.
The spherical mirrors we find in reality are usually less curved than those shown here in the section, so we can consider this rule to be true for existing mirrors. As for convex mirrors, the same reasoning must be followed, and the result will be the same; however, since the focal length is behind the mirror, unlike what happens with concave ones, the focal length is neglected.
Focal length also applies to lenses, but there is another change in the sign of the value due to double refraction: let the foci be considered positive outside the lens and negative in front of it. The focal length of a concave lens will be calculated using the following formula.
If, propagating from a star in the direction of the Earth, light passes near the Sun, then it will deviate somewhat, so that the segment does not lie on the same straight line with . In this case, from the Earth, the star will appear to be in a direction although the true direction will correspond to the line. The displacement of the apparent position of the star relative to its true position in the sky is characterized by an angle. This displacement can be calculated, but the theories of Newton and Einstein lead to different results. We have already indicated that Newtonian mechanics can be considered as a first approximation to Einstein's theory. The latter, so to speak, adds a certain correction to Newton’s law due to the curvature of space in the vicinity of matter. If the formula given on page 138 is replaced by the expression, then we should obtain orbits that will coincide with those calculated on the basis of Newtonian mechanics. The additional term corresponds to the replacement of Euclidean space (and not space-time) with a non-Euclidean one. It is the presence of this term that leads to a radical difference in the calculated values of the apparent displacement of the star in both theories. We are not able to reproduce on the pages
The experimental system is inspired by research into the famous invisible cloak popularized by Harry Potter. Instead of trying to camouflage an object in space, the system hides it from time to time. The findings are an important step forward in creating a complete space-time cloak, said study co-author Moti Friedman of Cornell University in New York. Physicists' success is based on the properties of the visible light spectrum and the fact that the colors that make it up move at different speeds.
this book necessary calculations, however, the results can be stated in a simple form.
If the light from a star passes at a distance from the center of the Sun, then the angular displacement visible from the Earth, according to Einstein's theory, will be right angles, where, as before, If the light passes near the surface of the Sun, then we can assume that We leave it to the reader to prove that this is equivalent to an angle of approximately ang. sec (see exercise 4 on page 151).
This cloak of temporary invisibility involves the propagation of a beam of green light into an optical cable. The beam passes through a lens, which splits it into two separate clicks - blue light, which travels slightly faster than the original green beam, and red light, which is slightly slower. The resulting difference between the speed of the two beams is increased by placing a transparent barrier.
Changing the direction of the light beam
After all, there is a temporary time difference between the red and blue rays in a fiber optic cable. However, it is on the order of 50 picoseconds, which is enough to insert laser light at a different frequency than the light in the cable. After a short-lived laser beam, the red and blue beams are reversed - the new barrier speeds up the red light and slows down the blue light, and the lens restores the original two light beams, creating a single green beam.
Newton's theory results in a displacement of right angles, that is, half of that required by Einstein's theory. The validity of one of the theories was to be revealed as a result of direct astronomical observations.
Oliver Lodge, in his article "The Nineteenth Century", gave a vivid illustration of how this test became the stimulus for the development of practical astronomy. Below is an excerpt from this article.
There is also a 40 picosecond laser emission that remains completely unobtrusive because it is not part of the photon of light being reconstructed. "This method is similar to a railroad crossing," said Robert Boyd and Chomin Shi of the University of Rochester in New York, and when a train approaches, cars stop at the crossing, creating something of a traffic jam. To an outside observer, the movement appears normal and there is no evidence of a train passing at the railroad crossing, and the next step in the study will be to increase the "time span" that masks the event.
“Let's take a thin silk thread and stretch it over a smooth table surface. Let's imagine a star at one end of the thread, the observer's eye at the other, and consider the thread as a ray of light emitted by the star. Now take a halfpenny piece and place it on the table near the thread at a distance of 10 feet from the end where the eye is. Then we will carefully move the coin until it moves a barely noticeable amount of an inch. Looking along the beam, we will see that it is no longer absolutely straight. In other words, the observer will see the star, the apparent position of which is characterized by the ray, slightly displaced. The scale is determined by the size of the coin, which is 1 inch in diameter. The coin characterizes the Sun, which is 1,380,000 km across. A distance of 10 feet between the eye and the Sun practically means that the observer is on the Earth, which on these scales is the size of a grain. As for the distance to
Scientists are working on theoretical foundations technologies that will allow large objects to become invisible. It is based on the idea of developing devices that generate special electromagnetic waves. They will merge with the waves falling on objects in such a way that their image is completely neutralized. This is a radically different technology from what has been developed so far for the invisibility of bodies. All of them focused on the properties and capabilities of metamaterials. New theory has several advantages over legacy concepts.
star located at the far end of the thread, then it has no meaning; on the same scale, the length of the filament to one of the nearest stars would be hundreds of kilometers. A displacement of an inch at a distance of 10 feet corresponds to an angle of sec, which coincides with the optical displacement predicted by Einstein for the case when a ray of light from a star almost touches the solar disk on its path through a telescope.”
One of them is the ability to disguise large objects. In addition, the technology can be used to work with various waves - for example, seismic or acoustic, which significantly expands the possibilities of its application. Doctors from the Karlsruhe Institute of Technology have created a material that can hide an object of observation in three dimensions. Researchers have demonstrated the concealment of a defect in a gold plate behind a new material. A defect with dimensions of several micrometers on a 150 nm gold plate is completely invisible at viewing angles of no more than 30 degrees from the vertical in all three dimensions.
Modern instruments and measurement methods have reached such a high level of perfection that measuring even such angular displacements as discussed above, or establishing the difference between two small angular displacements of the same order of magnitude, is quite within the capabilities of modern astronomers. Unfortunately, the only time when you can see a star in line with the Sun is during a total solar eclipse. In addition, reliable results cannot be obtained unless there are several bright stars. Fortunately, these conditions were met during the total solar eclipse of May 29, 1919. Two expeditions were organized: one was sent to Sobral (Northern Brazil), and the other to Principe Island in the Gulf of Guinea in order to obtain the necessary photographs. The history of these expeditions is described in detail by Eddington in his book Space, Time, Gravity. The expedition to Príncipe Island failed because cloud cover greatly hampered observation. In Sobral, the atmospheric conditions were excellent. Here, however, another difficulty was encountered that reduced the value of many photographs. Observations on Principe Island, taking into account possible experimental errors, gave an apparent displacement value in the range from 1.91 to 1.31 at Ch. sec, while observations at Sobral established a bias in the range of 2.10 and 1.86 at Ch. sec. During another total solar eclipse in 1922, a successful expedition was
Past advances in invisible materials were limited to either a single viewing plane or the object was invisible within a very narrow range of illumination. In general, metamaterials have the property of having negative permeability - dielectric, magnetic or optical. The new metamaterial is a complex structure of polymer rods several hundred nanometers thick. The polymer is processed in a special way using a laser to give it a specific structure and refractive index.
The researchers say there is no limit to the size of a hidden object, but it takes three hours to create a micron-sized experimental sample, and invisibility is provided in the light range of wavelengths of 1.4 microns or more. To create invisibility in the optical range, the thickness of metal rods should not exceed 10 nm, which is not yet available in modern technology laser processing. If a way can be found to shape sticks this thick, mass-producing invisible cloaks won't be so difficult.
For many readers, such a wide range of results may be disappointing. Those engaged in practical research must understand that experimental errors are inevitable: all that can be done in this case is to indicate the limits of error. It should be recalled that the conditions in which the expedition was forced to work are not as comfortable as the conditions of work in a stationary observatory, just as the combat conditions in which the field telephone service is located are naturally much less favorable than the operating conditions of the London Central Telephone Center . However, the results certainly speak in favor of Einstein's theory. If we are talking about a choice between Einstein's theory and Newton's theory, then there can be no doubt that Einstein's calculations are in better agreement with the results of observations solar eclipses than calculations based on Newtonian mechanics. But regardless of the specific observational evidence, it is important to remember that this deviation was not suspected until Einstein predicted it based on the theory of relativity. A theory that predicted a hitherto unknown phenomenon and then discovered it experimentally rests on a more solid foundation than a theory created to explain facts known from experience. This is mainly due to the fact that a whole set of hypotheses can be proposed to explain a given sum of facts. And no matter what modifications the theory undergoes in the future, nothing can overshadow the success that befell this prediction, made by Einstein in 1915, verified by astronomers during the eclipses of 1919 and 1922. and has now received universal recognition,
A man named John Mackie, an early Mason, taught a method in which anyone could become invisible. Another branch of the Rosicrucians, the Hermetic Order of the Golden Dawn, leaves manuscripts describing the ritual of invisibility. These manuscripts tell how to wrap oneself in a rag, which is described as a cloud. It is said that Blavatsky of the Theosophical Society witnessed this invisibility and even received the secret, after which she spoke with this practice several times before witnesses. Spiritualist literature in the United States shows that there is no doubt that they knew about the cloud and its creation.