|
|
TEXTS FOR READING COMPREHENSION
Text A.
Sir Isaac Newton (1643-1727) noticed the spectrum when he put a wedge of glass in front of a narrow beam of light entering a dark room through a hole in a window shutter. From this he realized the nature of white light and was able to explain the rainbow. The rainbow is, indeed, nothing but the white light of sun split up into colours of the spectrum by the drops of water falling in a shower.
If the seven spectrum colours are painted in seven sectors on a cardboard wheel it will appear almost white when spun round quickly. This provides another proof that white light is made up of these colours.
The mixing of colours. We know that in painting those colours which cannot be obtained by mixing are called the “primary” colours, and others are called “mixed” colours. An artist will tell you that red, yellow and blue are the primary colours, because he cannot make these from the others in his box of paints. He calls green a mixed colour because he can make it by mixing yellow and blue; he also makes violet from red and blue, and orange from yellow and red. If we use coloured lights instead of paints, we get different results, and find that red and green make yellow, and green and violet make blue. But there are really no “primary” colours; each colour represents light of a single wave length and any colour looks like a mixture of the two on either side of it in the spectrum.
Red paint is a substance that absorbs all the other colours except red, which it reflects. Green leaves absorb all the colours except green. Blue paint always reflects a certain amount of green, and so does yellow paint, and when you mix blue and yellow paint each pigment absorbs all the light from the other except the green that they have in common. When you mix lights together, all the colours seen together produce white. If you mix red and green, this is the same thing as cutting out the blue, and when you remove the blue from white light the opposite colour to blue, which is yellow, shows up.
The scientist using coloured lights calls red, green and violet his primary colours. The colour-painter and painter call red, yellow and blue their primary colours. If you mix all the coloured lights together, you get white, but all the coloured paints produce black. This is because the paints absorb colours, whereas lights produce them.
Exercises
I. Look through the text and give a title to it.
II. Find the definition of the term “primary colour”:
• It is a colour which reflects light.
• It is a colour which can be obtained from mixing.
• It is a colour which cannot be obtained from other colour.
III. Rearrange the sentences to make a summary of the text.
• Green is a mixed colour in painting.
• Red, green and violet are primary colours for coloured lights.
• White light may be split into seven spectrum lights.
• Isaac Newton understood the nature of white light.
• There are “primary” and “mixed” colours.
• Newton explained how the white light is split in a rainbow.
• “Primary” and “mixed” colours are considered different by painters and scientists.
• The paints absorb colours, lights produce them.
Text B.
By using small particles and high speeds scientists have proved that 186,000 plus or minus 90,000 still equals 186,000. Einstein’s second postulate of his special theory of Relativity, this basic law of physics, states that the speed of light is constant and independent of the motion of its source. New studies by several scientists suggested that the law might need revision; that the speed of light did vary with the movement of its source.
The problem might be stated something likes this: A car is travelling at night at a speed of 60 mph. The question is, what is the speed of the light being emitted by the headlights and the taillights. Einstein’s law says that the speed of light is always the same: it is always 186,000 miles per second.
No, the new evidence seemed to argue. The light from the headlight travels at the speed of light plus the speed of the car; the light from the taillight moves with the velocity of light minus the speed of the car.
An experiment was made. A moving source of light was selected whose own speed was measured against the speed of light. A positron (a positively charged electron) was set in motion in a reactor at a speed of roughly 90,000 miles a second. The laws of nuclear physics went to work.
When a positron collides with an electron, the two particles destroy one another, producing gamma rays. Gamma rays are actually a form of light, and their waves travel with its speed. The impact launches some gamma rays on a path in the direction of the positron’s flight, but others along an opposite path. The problem was to monitor the sequence of events accurately, both the speed of the gamma rays and the direction of their movement.
So the collision was arranged. The gamma rays liberated by the annihilated positron sped along their predicted paths either following or reversing the positron’s course. The extremely sensitive monitoring equipment used had no difficulty in determining whether or not the gamma rays travelled at speeds plus or minus 90,000 miles per second. Their speeds, within the experimental margin of error, were shown to be identical. That is, the speed of light is constant and independent of the motion of its source.
How did the scientists know that the gamma rays came from a positron destroyed in flight and not at rest? Gamma rays move away from a positron destroyed at rest always in the same straight line. The equipment accordingly was positioned so that it picked up only those gamma rays whose paths made an angle with each other of less than 180°. These were rays, then, resulting from a positron annihilated in flight.
The arrival times of the gamma rays were recorded at the ends of their respective paths by photomultiplier tubes which convert light impulses into electrical energy. The information was then transmitted to a coincidence counter which determines whether or not the impulses are detected within a given interval of time. This was how it was shown finally that the gamma rays had identical speeds.
Exercises
I. Look through the text and give a title to it.
II. Find the sentences which express the main idea of the text.
• Several scientists suggested that the law about the speed of light might need revision.
• Some think that the light from the headlights of a car travels at the speed of light plus the speed of the car.
• The speed of light is constant.
• Some think that the light from the taillights of a car travels at the speed of light minus the speed of the car.
III. Rearrange the sentences to make the summary of the text.
1. The arrival times of the gamma rays were recorded, it was proved that the gamma rays have identical speeds.
• Einstein in his theory of Relativity states that the speed of light is constant.
• An experiment with gamma rays was made.
• The speed of light of the headlights of a travelling car might be more than the speed of light of the taillights.
• Some scientists thought that the speed of light is not constant.
• The experiment proved that Einstein was right.
Text C.
Mars, the fourth planet from the Sun after Mercury, Venus, and the Earth, has been studied more thoroughly than any other planet except the Earth. US space exploration began in 1964, when Mariner 4 flew by Mars and sent back to the Earth several indistinct pictures of a cratered surface. This was followed by two additional US flybys in 1969 and by the Mariner 9 orbiter in 1971. The USSR was the first to reach Mars in 1971, there were 4 other vehicles in 1974. Then, in the summer of 1976, the Viking project placed two elaborately instrumented vehicles on Mars’s surface and left two others in orbit to make global observations. Of particular importance for understanding the geology of Mars are the orbiter pictures, which cover the entire planet at a resolution of around 200m, and which also cover extensive areas at higher resolutions, ranging down to about 10m.
Mars has followed a distinctively different evolutionary path from those of the Moon or the Earth. On the Moon, volcanic activity ceased around 3 billion years ago, and since that time, the surface has remained essentially unchanged except for the occasional impact crater. Mars appears, however, to have been volcanically active throughout its history, and its large volcanoes are probably still active. Moreover, the surface has been modified to varying degrees by the wind, and possibly by water and ice also.
Despite these superficial resemblances to the Earth, the differences between the Earth and Mars are enormous. The Earth’s geology is dominated by the effects of plate tectonics. The motions of the plates control the positions of continents, mountain chains, and ocean depth and affect the style of crustal deformation and the type, periodicity, and location of volcanic activity. Furthermore, the surface of the Earth is extensively modified by running water, which redistributes materials and eliminates extremes of relief. In contrast, the crust of Mars is relatively stable.
There are some properties of Mars that might affect geologic processes. The equatorial radius of 3,390 km is a little over half that of the Earth and close to twice that of the Moon. The axis of rotation is inclined 250 to the ecliptic, which means that the planet has seasons; however, because of the relatively high orbital eccentricity (0.097), there is a seasonal asymmetry, with summers in the south being shorter and hotter than those in the north.
Exercises
I. Look through the text and give a title to it.
II. Which of the following statements characterize the geology of Mars:
• Volcanic activity there ceased about 3 billion years ago.
• Volcanic activity there is known throughout its history.
• Its surface remained practically unchanged.
• Its surface has been changed by the wind and possibly by water and ice.
• Its surface is changed by running water which brings changes to its relief.
III. Rearrange the sentences to make the summary of the text.
• Mars’s surface has been modified by the wind, water and ice.
• Mars has been thoroughly studied.
• There are differences between Mars, the Earth and the Moon.
• Different countries took part in the exploration of Mars.
• The equatorial radius of Mars is about half of that of the Earth.
• Mars’s volcanoes are probably still active.
• Mars has seasons, but there is a season asymmetry due to the high orbital eccentricity.
Text D.
Man’s prime need in his environment is for water, and wherever a number of people live together in a community a supply of potable water is required. In primitive civilization the remedy to pollution problems was to move the community to a new unspoilt site, but in more advanced communities this solution becomes impracticable. Water thus can be considered as the most important raw material of civilization since without it man cannot live and industry cannot operate. The concept of water as a natural resource is essential as growing populations and industrial developments demand ever-increasing supplies of water.
Water quality control has a long history, and archeological investigations in the Middle and Far East have revealed towns with sewer systems built several thousand years B.C. The Romans constructed great aqueducts and sewers for the city of Rome at the time of Christ, but in the rest of Europe little was done to promote public health and improve the environment for many centuries. In England attempts were made by Richard II in 1388 and Henry YIII in 1531 to prevent water pollution due to cesspool discharges. Although the larger towns were provided with sewerage systems which were used only for the conveyance of surface water, discharge into them of domestic wastes was forbidden until 1815. In 1847 a law was passed to enforce discharge of wastes to sewers which had disastrous results for the inhabitants of London. London’s sewers drained to the Thames from which much of the city’s water was obtained, and because of the age and poor state of repair of many of the sewers their contents leaked into the water-bearing strata which was the other main source of water. As a result water supplies became contaminated by sewage and a series of cholera outbreaks demonstrated the connection between diseases and polluted drinking water.
The outbreak of 1854 in which there were 10,000 cholera deaths in a population of 2.5 million provided conclusive evidence of the connection. Conditions similar to those which existed in London were found in other parts of the world following the great expansion of urban development during the Industrial Revolution.
Exercises
I. Look through the text and give a title to it.
III. Arrange the sentences in their logical order according to the text.
• A series of cholera outbreaks demonstrated the connection between diseases and polluted drinking water.
• Man’s prime need in his environment is for water.
• Water quality control has a long history.
• Water thus can be considered as the most important raw material of civilization.
• In England attempts were made to prevent water pollution due to cesspool discharges.
IV. Find the sentence which expresses the main idea of the text.
• The water quality control has a very long history starting several thousand years B.C.
• Water is the main raw material of civilization because without it man cannot live and industry cannot operate.
• The pollution water problems were closely connected with the Industrial Revolution.
Text E.
Neutrons are the “undercover agents” of the physical world. Generally invisible even in sophisticated detectors, these particles are nevertheless essential to current understanding of nuclear interactions in experiments that probe the structure of protons. Invented in 1931, the neutrino was not discovered until 1956, but recent evidence suggests that neutrinos might make up the larger part of the mass of the Universe. If proven these latest results will deeply affect ideas concerning the beginning and end of the Universe.
The Austrian physicist Wolfgang Pauli first postulated the existence of neutrinos to account for some puzzling features of the beta-decay of atomic nuclei. He invented a particle, which he said must interact very weakly with other matter (otherwise it would already have been observed); it must be electrically neutral; and must have intrinsic angular momentum (spin) of a precise amount.
The invention of this particle, which Enrico Fermi later called the neutrino, solved the problem concerning the beta-decay spectrum, as the electron and the neutrino could share in an infinite number of ways the kinetic energy not taken up by the nucleus. Finally, Pauli suggested that the unseen particle had zero mass when at rest, as, within the accuracy of the experiments, the end point of the spectrum was consistent with the electron’s taking away all the available energy.
But it was not until 1956 that Frederick Reines and Clyde Cowan found direct evidence for the existence of the neutrino in an experiment at a nuclear reactor.
Frederick Reines and Clyde Cpwan looked for interactions between neutrinos, emerging from beta-decays within the reactor, and protons in a large tank of liquid scintillator. This material flashes light when electrically charged particles pass through it, and Reines and Cowan were thus able to detect the positrons - the positively charged anti-particles of electrons - created when neutrinos interacted with protons and converted them to neutrons. They were also able to detect gamma rays emitted as the neutrons produced were captured by other nuclei.
Since 1950s several groups of physicists have shown that neutrinos come in more than one variety, depending on the other particles involved in the interactions. For example, in the beta-decay of a neutron, an electron-neutrino accompanies the electron produced. More specifically, to balance the book-keeping, it is an electron-antineutrino, the antimatter counterpart of the neutrino.
There is good evidence from a number of experiments that the mass of the neutrino - whichever type - is certainly very small, but no experiment has ever conclusively shown it to have zero rest mass.
Exercises
I. Look through the text and give a title to it.
II. Re-arrange the sentences to make a summary of the text.
• Suggestions concerning the properties of the neutrinos.
• The experiment of F.Reines and C.Cowan.
• The mass of the neutrino.
• The role the neutrino might play in making up the mass of the Universe.
• Varieties of neutrinos.
• The discovery of the neutrino by Frederick Reines and Clyde Cowan.
• Prediction of the existence of neutrinos by Wolfgang Pauli.
III. Find the statement that does not correspond to the contents of the text.
• The invention of the neutrino solved the problem concerning the beta-decay spectrum.
• The fusion reactions that cause the sun to shine produce neutrinos.
• The mass of the neutrino is certainly very small, but no experiment has ever shown it to have zero rest mass.
• For years, some scientists have wondered if mass-bearing neutrinos could make up part or all of the cosmic “dark matter”.
• Neutrinos come in more than one variety, depending on the other particles involved in the interaction
EINSTEIN’S RESEARCHES ON THE NATURE OF LIGHT
«For the rest of my life I will reflect on what light is!»
A. Einstein, 1917
The fundamental contributions were made by Albert Einstein toward our present-day understanding of the nature of light. In our time of ever-increasing spe-cialization, there is a tendency to concern ourselves with1 relatively narrow scientific problems. The broad foundations (ôóíäàìåíòàëüíûå îñíîâû) of our present-day scientific knowledge and its historical development tend to be forgotten too often. This is an unfortunate trend, not only because our horizon becomes rather limited and our perspective somewhat distorted, but also because there are many valuable lessons to be learned in looking back over the years during which the basic concepts and the fundamental laws of a particular scientific discipline were first formulated.
To scientists and nonscientists alike, the name Albert Einstein is associated with a theory that has profoundly revolutionized man’s ideas of space and time. His theory of relativity implied as basic a change in our conception of the universe as that which was brought about by Newton’s theory of universal gravitation or Kepler’s theory of the planetary system. For this work alone, Einstein will certainly always be remembered as one of the greatest geniuses of all times. Einstein also made most ba-sic contributions to our understanding of the nature of light and radiation in general.
Early theories. In the seventeenth century, two theories were put forward about the nature of light: the wave theory, whose chief proponents (çàùèòíèê, ñòî-ðîííèê) were Robert Hooke and Christian Huygens, and the corpuscular (or emis-sion) theory, put forward by Isaac Newton. According to the wave theory, light con-sists of rapid vibrations that are propagated in an elastic ether in a somewhat similar manner as a disturbance is propagated on the surface of water. According to the cor-puscular theory, on the other hand, light is propagated from a luminous body by minute particle2. The wave theory, as then formulated, appeared to be incapable of explaining the phenomenon of polarization, discovered by Huygens himself in studying the refraction of light by crystals. Newton, on the other hand, was able to account for3 polarization on the basis of his corpuscular theory. It was largely for this reason that the wave theory was rejected for over a century in favor of the corpuscular theory.
In 1801 Thomas Young discovered the principle of interference of light. Seven-teen years later Augustin Fresnel showed in a celebrated memoir (íàó÷íàÿ ñòàòüÿ) that, by combining Young’s principle of interference with a basic postulate of Huy-gens’s theory, one is led to a wave theory of light that explains diffraction of light, a phenomenon that was not comprehensible on the basis of Newton’s corpuscular theory. Within a few years after the publication of Fresnel’s memoir and after expe-rimental demonstrations of certain unsuspected predictions of his theory, Fresnel’s wave theory became generally accepted and Newton’s corpuscular theory fell into oblivion (ïðåäàíà çàáâåíèþ).
The formulation of the wave theory of light culminated in the work of James Clerk Maxwell, who succeeded in 1865 in embodying all the laws of electricity and magnetism then known into a celebrated set of differential equations – now called Maxwell’s equations. One of the consequences of these equations was a prediction that time-dependent electric and magnetic effects are transmitted from one region of space to another by means of waves – known now as electromagnetic waves. The speed of these waves in free space could be calculated from the results of purely elec-trical measurements, and it turned out to be of the order of magnitude of the speed of light, as then known from other experiments. This led Maxwell to conjecture that light waves are electromagnetic waves. In 1888 Heinrich Hertz demonstrated the ex-istence of electromagnetic waves experimentally. We may thus summarize this part of our brief historical introduction by saying that, toward the end of the nineteenth century, it appeared firmly established that light is an electromagnetic wave pheno-menon. Rather independently of the developments just mentioned, investigations were carried out concerning thermal or heat radiation, which eventually also turned out to be of fundamental importance for elucidating (ðàçúÿñíÿòü; ïðîëèòü ñâåò íà…) the nature of light.
In the period 1814–1817 Joseph Fraunhofer discovered dark lines in the solar spectrum, which have since been named after him. On the basis of experiments by Robert Bunsen and Gustav Kirchhoff, they were interpreted around 1860 as ab-sorption lines of certain gases in the solar atmosphere. In the course of his investiga-tions of the solar spectrum, Kirchhoff derived from thermodynamics a number of fundamental results relating to radiation in thermal equilibrium with bodies at a fixed temperature. Even under equilibrium conditions, when the system is thermally insu-lated from its surroundings, the bodies will emit and absorb radiation, or as we say these days, there will be interaction between matter and the radiation field. The ca-pacity of a body to emit and absorb radiation at some fixed frequency may be charac-terized by certain quantities known as the emission coefficient and the absorption coefficient. One of the laws, which Kirchhoff derived in 1859, asserts that, under equilibrium conditions, the ratio of the emission and the absorption coefficients is in-dependent of the nature of the bodies that interact with the radiation field.
4. Particle aspects of radiation. Even though Planck’s introduction of the con-cept of an energy quantum led eventually to one of the greatest scientific revolutions of all times, his theory did not at first attract much attention. One of the first scientists who clearly recognized that Planck’s discovery initiated a new era4 in physics was a young man, Albert Einstein, who around that time – in 1902 at the age of 23 was appointed to a post at the Swiss Patent office. His appointment carried the title «Technical Expert, Third Class». His three papers were published, in 1905, having all been submitted within a period of only three and a half months. Einstein’s papers: (1) the particle nature of radiation, (2) the theory of Brownian motion, and (3) the special theory of relativity are acknowledged as masterpieces and the starting point of a new branch of physics.
The first of these papers has, in translation, the title: «On a heuristic point of view concerning the creation and conversion of light». It is this paper that Einstein himself referred to as «very revolutionary». In modern textbooks it is usually referred to as «Einstein’s paper on the photoelectric effect». Actually, this paper contains appre-ciably more. In fact, Einstein’s whole discussion of the photoelectric effect covers less than four pages; but, as in most of his writing, Einstein was able to get to the root of a problem5 in a few lines, with simple language that was remarkably free of com-plicated mathematics.
Essentially what Einstein did in this paper was to put forward a great deal of evidence that not only do the processes of emission and absorption of radiation take place in discrete amounts of energy (as appears to have been established by Planck) but that radiation itself behaves under certain circumstances as if it consisted of a col-lection of particles, which in modern language are called photons. Thus in this paper Einstein reintroduced a corpuscular theory of light – first advocated by Newton in the 17th century. In the introduction to his paper, Einstein discusses the success of the wave theory of light, which deals with continuous functions in space6. Then Einstein goes on to say that nevertheless it is possible that this theory will lead to a contradic-tion with experience if it is applied to the phenomena of generation and conversion of light. He then continues as follows: «In fact it seems to be that the observations on blackbody radiation, photoluminescence, the production of cathode rays by ultravio-let light, and other phenomena involving the emission or conversion of light, can be better understood on the assumption that the energy of light is distributed disconti-nuosly7 in space. According to the assumption considered here, when a light ray start-ing from a point is propagated, the energy is not continuously distributed over an ev-er-increasing volume8, but it consists of a finite number of energy quanta9, localized in space, which move without being divided and which can be absorbed or emitted only as a whole».
Another example that Einstein gave in this paper in support of his view regard-ing the corpuscular nature of radiation was, as already mentioned, the photoelectric effect. This is the phenomenon of ejection of electrons from a metal when electro-magnetic radiation of short enough wavelength impinges on the metal surface. The effect was discovered in 1887 by Heinrich Hertz in the course of experiments re-ferred to earlier, which played a decisive role in confirming the correctness of Max-well’s electromagnetic theory of light. In retrospect, there is some irony in this situa-tion, since later, when the photoelectric effect was studied quantitatively, it was not possible to reconcile it with Maxwell’s electromagnetic theory.
In 1909, four years after his «photoelectric paper», «Einstein published a paper» with the title «On the present status of the problem of radiation», which became another milestone in the development of physics. In this publication Einstein showed, again by characteristically simple arguments typical of so much of his work, that Planck’s radiation law itself implies that the radiation field exhibits not only wave features but also corpuscular features. This result was the first clear indication of the so-called wave particle duality that many years later became an accepted feature of modern quantum physics.
5. Elementary processes of interaction between radiation and matter. Dur-ing the next few years Einstein concentrated his efforts in different directions, and he developed his general theory of relativity. But in 1917 he returned to the radiation problem once again, and he published another fundamental paper in this field. By that time much progress had been made toward the understanding of the spectrum of atomic elements, chiefly as a result of some work by Niels Bohr. Before discussing the 1917 paper of Einstein, it may be useful to review briefly some of the back-ground. In 1911, Ernest Rutherford put forward a model of the atom according to which the atom consists of a small, heavy, charged central nucleus surrounded by a charge distribution of the opposite sign. However, the distribution of the charge was not understood. Bohr, in a well-known paper published in 1913, assumed that the atom can exist permanently only in one of a series of states – known as stationary states – characterized by discrete values of the energy. When the atom emits or absorbs radiation it undergoes a transition from one such stationary state to another.
6. The Bose-Einstein statistics and matter waves. Successful as Einstein’s notion of quanta of radiation field was in elucidating various phenomena involving the interaction of light and matter, many puzzles surrounded it. All the derivations of Planck’s radiation law, including Einstein’s 1917 derivation, appealed at some point to classical electromagnetic theory. Yet the quantum features of the radiation field, which as Einstein showed, are implicit in Planck’s law, are in direct contra-diction with the classical theory. Einstein himself was well aware of these difficulties, and he stressed over and over again the need to formulate a basically new theory that would fuse the wave features and the particle features of radiation. Such a theory, namely, modern quantum mechanics, was indeed formulated about eight years after the publication of the paper by Einstein that we have just discussed.
Notes:
• in our time of ever-increasing specialization, there is a tendency to concern ourselves with
• minute particles
• account for
• initiated a new era
• was able to get to the root of a problem
• continuous functions in space is distributed discontinuously
• the energy is not continuously distributed over an ever-increasing volume
• a finite number of energy quanta
• çäåñü: â íàøå âðåìÿ ðîñò ñïåöèàëèçàöèé – ýòî òåíäåíöèÿ ê ðåøåíèþ
• ìåëü÷àéøèå ÷àñòèöû
• îáúÿñíÿòü
• îòêðûë íîâóþ ýðó
• ñìîã âíèêíóòü â ñóòü ïðîáëåìû
• ôóíêöèè, íåïðåðûâíûå â ïðîñòðàíñòâå ðàñïðåäåëÿåòñÿ äèñêðåòíî (íåðàçðûâíî)
• ýíåðãèÿ íå ðàñïðåäåëÿåòñÿ íåïðåðûâíî â çàïîëíÿåìîì ñâåòîì îáúåìå
• êîíå÷íîå ÷èñëî êâàíòîâ ýíåðãèè
HISTORY OF THE PRODUCTION OF
OPTICAL INSTRUMENTS
• The word «optics» is of Greek origin, and it relates to what is seen, and optical instruments historically have been aids to vision. Though simple lenses had been in use as magnifiers for over a thousand years, and though eye-glasses had been developed in the 14th century, optical engineering1 began in the 17th century with the development of the first precision optical instrument, the telescope. The microscope was developed almost simultaneously. Because manufacturing problems were little understood, and available glass was poor2 early instruments were primitive. Modern instrument-making industry is equipped with a great variety of optical instruments. It is only by optical methods and by making use of special optical systems that one can make precise measurements.
• The history of production of fine (òî÷íûé) optical instruments is connected with the name of Carl Zeiss. The products and the name Zeiss enjoy an outstanding reputation3 all over the world. Carl Zeiss was born in Weimar, 1816. The German industrialist gained a worldwide reputation as a manufacturer of fine optical instruments. In 1846 Zeiss opened a workshop in Jena for producing microscopes and other optical devices. Realizing that improvements in optical instruments depended on advances in optical theory4, he engaged a research worker Ernest Abbe, a physics and mathematics lecturer, professor of the University of Jena. In 1866 he became Zeiss’s partner. Later they engaged Otto Scott, a chemist, who developed about 100 new kinds of optical glass and numerous types of heat-resistant glass.
• Right from the beginning of his collaboration with Carl Zeiss in the mid-1880s, Ernst Abbe devoted a great deal of attention to optical materials. His detailed studies were focused on not only the optical properties of the types of glass then available, but also on those of liquids and minerals. The interdisciplinary collabora-tion of the chemist Otto Scott and the industrial physicist Ernst Abbe offered a great opportunity to the then emerging optical industry in Germany. Despite all the good results obtained with the new glass types, Abbe soon realized that he would have to continue to include crystals as optical materials in his studies. He developed the apochromat microscope objectives and used the mineral fluorite. These objectives were indeed one of the most important innovations in the field of microscope design. Fluorite is a mineral which occurs very frequently in nature. From the crystallograph-ic viewpoint, the cubic crystal symmetry of fluorite is of importance for its use as a material in an imaging system.
• Apochromats are highly corrected optical systems5 providing maximum opti-cal quality and are used in microscopy and astronomy. Ernest Abbe was sure that the availability of optical materials must be safeguarded by synthesis6. In the 1930s, a laboratory for growing crystals was established at the Zeiss plant. However, it was only after Stockbarger in the USA had further developed the method of growing fluo-rite from vacuum melts7 for industrial use that fluorite was produced at Zeiss in the second half of the 1950s for use in its own instruments, achieving independence from natural deposits.
In 1945 US forces (army) evacuated the board of management and about 100 scientists and technicians of the Carl Zeiss firm (Jena) to West Germany, where it was firmly reestablished; and it was transformed into a powerful industrial enter-prise; later the Carl Zeiss firm became a world leader in optics. The history of the company Carl Zeiss is full of examples of extremely successful interaction between experimental science and instrument manufacture.
Notes:
1. optical engineering îïòè÷åñêàÿ òåõíèêà
2. available glass was poor äîñòóïíîå ñòåêëî áûëî ïëîõîãî
êà÷åñòâà
3. enjoy an outstanding reputation ïîëüçóåòñÿ âûäàþùåéñÿ ðåïóòàöèåé
4. advances in optical theory ïðîãðåññ â îïòè÷åñêîé òåîðèè
5. highly-corrected optical systems òî÷íî ñêîððåêòèðîâàííûå
îïòè÷åñêèå ñèñòåìû
6. . vacuum melts âàêóóìíàÿ ïëàâêà
7 must be safeguarded by synthesis äîëæíî áûòü ïîäñòðàõîâàíî
ïðîèçâîäñòâîì ñèíòåòè÷åñêèõ ìàòåðèàëîâ
METROLOGY
• Metrology, the science of measurement. From three fundamental quantities, length, mass, and time, all other mechanical quantities – e. g., area, volume, acceleration, and power – can be derived (ïîëó÷àòü, èçâëåêàòü). A comprehensive system of practical measurement should include at least three other bases, taking in the measurement of electromagnetic quantities, of temperature, and of intensity of radiation – e. g., light.
• Accordingly, the 11th General Conference of Weights and Measures in 1960 adopted six quantities and units as the bases on which was established the International System of Units. Since 1887 many national standards laboratories have been founded to set up and maintain standards of measurement, both for the six basic quantities and for their systematic derivatives. They also do attendant test and verifi-cation work for science and industry. Examples are the National Bureau of Standards (NBS) in the United States, the National Physical Laboratory (NPL) in the United Kingdom, and similar bodies2 in many other countries.
3. The international metric organization created by the Metric Convention of 1875 (amended3 in 1921) also has a central laboratory, the International Bureau of Weights and Measures, at Sevres (near Paris). It has duties analogous to those of the national laboratories but is concerned especially with the international coordination of all scientific work relating to the maintenance and improvement of the metric sys-tem of units and standards. This organization acts under the authority of the Gener-al Conference of Weights and Measures with the aid of an elected executive body, the International Committee of Weights and Measures, which meets every year.
Notes:
1. a comprehensive system óíèâåðñàëüíàÿ ñèñòåìà
2. similar bodies çäåñü: ïîäîáíûå îðãàíèçàöèè
3. amended óëó÷øàòü; èñïðàâëÿòü, âíîñèòü
ïîïðàâêè
4. executive body èñïîëíèòåëüíûé îðãàí
METRIC SYSTEM AND ITS ORIGIN
• Metric system, international decimal system of weights and measures, based on the metre for length and the kilogram for mass. The idea of a universal system of measures and weights dates from long ago1, but it was realized only two centuries ago. The metric, or decimal system was worked out by the French Academy of Sciences in 1791 and was adopted in France in 1795 and, by the late 20th century, was used officially in almost all nations.
• The French Revolution of 1789 provided the opportunity to pursue (ïðåòâîðèòü) the frequently discussed idea of replacing the confusing welter2 of traditional but illogical units of measure with a rational system based on multiples of 103. In 1791 the French National Assembly directed (äàëà ðàñïîðÿæåíèå) the French Academy of Sciences to address (çäåñü: îáðàòèòü âíèìàíèå) the chaotic state of French weights and measures. It was decided that the new system would be based on a natural physical unit to ensure immutability. How were the units for length and weight de-fined then? Two French scientists who were given the task to define these units, took one fourth of the distance from the North Pole to the Equator on the geographical me-ridian which is running through Paris (the distance from Dunkirk in France to Barce-lona in Spain) and divided it into ten million equal parts. One of these parts was called a metre or «measure». The academy settled on the length of 1/10 000 000 of a quadrant of a great circle of the Earth, measured around the poles of the meridian passing through Paris. An arduous six-year survey to determine4 the arc of the meridian from Barcelona, Spain, to Dunkirk, Fr., eventually yielded a value of 39,7008 inches for the new unit to be called the metre, from Greek metron, meaning «measure».
• All other metric units were derived from the metre, including the gram for weight (one cubic centimetre of water at its maximum density) and the litre for capacity (one-thousandth of a cubic metre). Greek prefixes were established for multiples of 10, ranging from pico- (one-trillionth) to tera- (one trillion) and including the more familiar micro-(one-millionth), milli-(one- thousandth), centi-(one-hundredth), and kilo-(one thousand). Thus, a kilogram equals 1 000 grams, a millimetre 1/1 000 of a metre. In 1799 the Metre and Kilogram of the Archives, platinum embodiments of the new units, were declared the legal standards for all measurements in France, but the motto of the metric system expressed the hope that the new units would be «for all people, for all time».
• Not until 1875 did an international conference meet in Paris to establish an International Bureau of Weights and Measures. The Treaty of the Metre signed there provided for a permanent laboratory in Sevres, near Paris, where international standards are kept, national standard copies inspected, and metrological research con-ducted. The General Conference of Weights and Measures, with diplomatic representatives of some 40 countries meets every six years to consider reform. The conference selects 18 scientists who form the International Committee of Weights and Measures that governs the Bureau.
• For a time, the international prototype metre and kilogram were based, for convenience, upon the archive standards rather than directly upon actual measure-ment of the Earth. Definition by natural constants was readopted in 1960, when the metre was redefined as 1,650 – 763.73 wavelengths of the orange-red line in the krypton-86 spectrum, and again in 1983, when it was redefined as the distance tra-velled by light in a vacuum in 1/299,792,458 second. The kilogram is still defined as the mass of the international prototype at Sevres.
• In the 20th century the metric system generated derived systems needed in science and technology to express physical properties more complicated than simple length, weight, and volume. The centimetre-gram-second (CGS) and the metre-kilogram-second (MKS) systems were the chief systems so used until the establish-ment of the International System of Units.
• Russian scientists played a great part in the spreading of the metric system in Russia as well as in other countries. As far as in5 1867 D.I. Mendeleyev addressed Russian scientists to help to spread the decimal system. The project of the law about the use of the metric system in Russia was also worked out by D.I. Mendeleyev.
It should be said, however, that up till6 the end of the 19th century different units of measurement were used in various countries. In our country the metric system was adopted in 1918, soon after the Great October Socialist Revolution. Now it is adopted by most of the countries. None of the systems of the past can be compared in simplicity to that of our days.
Notes:
1. dates from long ago âîçíèêëî äàâíî
2. the confusing welter íåðàçáåðèõà (ïóòàíèöà)
3. multiples of 10 êðàòíûå äåñÿòè
4. an arduous six-year survey ñëîæíàÿ øåñòèëåòíÿÿ ñúåìêà
to determine ïî îïðåäåëåíèþ
5. as far as in åùå â
6. up till âïëîòü äî