44730

Modals + Perfect Infinitives. Subjunctive Mood. Conditional Sentences

Конспект урока

Иностранные языки, филология и лингвистика

By closer observtion of the spectrum however we find tht the spectrum is crossed by n immense number of fine drk lines mounting to mny thousnds. When we investigte the drk lines in the spectrum of the Sun we find tht these correspond line by line to the spectr emitted in the lbortory by vrious elements iron clcium hydrogen etc. From this it follows tht the light from the Sun must hve gone through clouds of these toms somewhere nd in respect to such substnces s iron or clcium or most other elements this must hve hppened on the Sun...

Английский

2013-11-13

56.05 KB

1 чел.

4

UNIT 18

Grammar:  1. Modals + Perfect Infinitives

. Subjunctive Mood

. Conditional Sentences

TEXT 18 A

THE COLOUR SPECTRUM

Light brings us the news of the Universe. Coming to us from the Sun and the stars it tells us of their existence, their position, their movements, their constitutions and other matters of interest.

The first step in the acquirement of this knowledge is made when we use a prism to analyze the light. In every case we observe a continuous spectrum of colours running from red to violet in the order of the colours of the rainbow.

By a closer observation of the spectrum, however, we find that the spectrum is crossed by an immense number of fine dark lines, amounting to many thousands. To each of these lines there corresponds a definite wavelength and a definite intensity. The explanation of the phenomenon can be based on absorption of radiation. When in the laboratory, a substance is vapourized and made luminous, the light it emits appears as a collection of isolated lines and is characteristic of the substance. No two substances yield the same line spectrum and consequently the chemical nature of substances can be determined spectroscopically. Thus glowing atomic hydrogen is characterized by a bright line in the red and since it is exhibited by nothing but hydrogen, it serves to disclose the presence of atomic hydrogen wherever it occurs.

When a beam of light which, if analyzed, would form a continuous spectrum, passes through a less brightly glowing vapour, which, acting alone, would give a line spectrum, the spectrum formed consists of a continuous background on which dark lines appear exactly in the positions of the bright lines which the interposed vapour would give by itself. The glowing vapour absorbs, from the light passing through it, precisely those colours which it can itself emit.

When we investigate the dark lines in the spectrum of the Sun, we find that these correspond line by line to the spectra emitted in the laboratory by various elements, iron, calcium, hydrogen etc., brought to the conditions of luminous gases.

From this it follows that the light from the Sun must have gone through clouds of these atoms somewhere and in respect to such substances as iron or calcium, or most other elements, this must have happened on the Sun because there is no other part of the path of the light where substances can be brought to the state of a luminous gas.

The radiation emitted by the Sun would have given a complete spectrum were it not that on its way to us it has passed through an atmosphere surrounding the Sun and containing the various elements in the form of gases. These gases themselves must be luminous and be emitting light of the very frequencies which we suppose them to have been absorbing and therefore causing black lines to appear in the spectrum.

The hot interior of the Sun would have given a complete spectrum but the cooler outer layers absorb the radiations of various wavelengths, thus producing the dark lines. These prove conclusively that the elements that are found on the Earth are found also in the Sun and stars.

We can use the relative intensities of the lines due to different elements to obtain some fairly reliable conclusions about the abundance of each element. If, for instance, we were to double the amount of one element in the Sun, leaving the amounts of the other elements unaltered, we shоu1d find that the intensities of the lines of the particular element would be relatively strengthened. It is by means of such considerations that we can determine the relative abundance of this or of that element in the Sun or in a remote star.

"We can, moreover, not only identify the chemical elements in the atmosphere of the Sun and the stars but draw conclusions concerning the temperature in their atmospheres. Astronomical spectra represent conditions which range in temperature from a few degrees above absolute zero to 100,000° or even more in the atmospheres of the hottest stars. For the Sun the central temperature is estimated to be of the order of 20,000,000° C.

Of all the results of stellar spectroscopy, however, the most interesting is the uniformity of distribution of the chemical elements throughout the Universe. It must have been a revelation to the earlier astronomers when they discovered in the Sun the same familiar substances —hydrogen, iron, calcium and the rest —which they knew on the Earth. Their belief in the uniformity of the chemical elements must have been strengthened when several mysterious spectral lines turned out to be produced by the newly discovered gas, helium. The principle of uniformity of chemical elements means that the atomic building blocks of the Universe are the same throughout space.

Answer the questions:

  1.  What news of the Universe does light bring us?
  2.  What do we observe when we use a prism to analyze the light?
  3.  What phenomenon can be based on absorption of radiation?
  4.  What do we find when we investigate the dark lines in the spectrum of the Sun?
  5.  What conclusion can be drawn from this observation?
  6.  When would the radiation emitted by the Sun have given a complete spectrum?
  7.  What fact proves conclusively the existence of the same elements on the Earth and in the Sun and stars?
  8.  How can we obtain reliable conclusions about the abundance of each element?
  9.  Can we draw conclusions concerning the temperature in the atmosphere of the Sun and the stars?
  10.  What does the principle of uniformity of chemical elements mean?

EXERCISES

I. Translate the following verbs paying attention to the prefixes.

estimate

charge

value

overestimate

overcharge

overvalue

underestimate

undercharge

undervalue

II. Translate the sentences paying attention to the “to be + adjective + preposition” structures.

1. It is characteristic of the kinetic theory of heat that all its statements are of this statistical kind.

2. The transformation occurs rapidly, as is characteristic for a radioactive decay with a large energy release.

3. These are errors which are characteristic of precise measuring system.

4. Such energy is typical of a cyclotrone.

5. The author's figures are not indicative of the role played by the receiving aerial as a link in the whole chain.

6. The equation 24 takes the following form, which is typical of many electrical integrating circuits.

III. Translate the sentences paying attention to the meaning of the word “matter”.

1. Early experimentors worked without satisfactory theory to explain the structure of matter.

. Cathode rays can penetrate matter very easily.

3. The subject matter of statics is to study bodies at rest.

4. The purpose of this chapter is to exemplify the subject matter of this book.  

5. To repeat the experiment was a matter of several hours.

6. The penetrating nature of the X-rays was a matter of great interest for early workers in this field.

7. Building a transistor receiver is a relatively easy matter.

8. As a matter of fact, the variation in wavelengths is the principal distinction between the different types of electromagnetic radiations.

9. No matter how accurate the measuring device may be, repeated readings will not be the same.

10. Solids maintain their sizes and shapes no matter where they are placed.

11. No matter what improvements are made, it will not be possible for the vehicle to considerably exceed the speed of its own exhaust.

IV. Translate the sentences paying attention to the verbs in bold type.

yield

 1. It is evident that thermonuclear fusion reactions can yield propellant temperatures and performance far beyond that available at present by any other means.

2. To be efficient, a propellant should have a large heat of combustion to yield high temperatures.

3. Research on nuclear rockets may yield information useful to the construction of such a device.

4. The discovery of X-rays has yielded certain branches оf medicine, radiology, radiotherapy and crystallography.

identify

5. Some special device was used to identify the position of the emitted beam.

6. We saw earlier how the energy contained in an assembly of molecules can be identified with the kinetic and potential energies of rotation, vibration and molecular interaction.

V. Translate the sentences paying attention to the meanings of the word “but”.

1. At that time aerodynamics was a new but very important science.

2. Since heat is not a substance but a form of energy, we cannot measure it directly in pounds or litres, but must measure it by the effect it can produce.

. We study every day in the week but Sunday.

4. Several years ago the centigrade scale was in common use in all but English-speaking countries.

5. Our Sun is but a star of our Milky Way, which is but one of many galaxies.

6. The tailless missile generally involves but one set of control surfaces.

7. Heat energy is nothing but the energy of motion of the molecules of which matter is composed.

8. Life is nothing but an endless series of chemical reactions.

9. But for the development of the helicopter into a practical aircraft, there is no doubt that the autogyro would still be much used.

10. The accuracy and reliability of his method were so obvious that we could not but accept it.   

VI. Translate the sentences paying attention to the meanings of the verbs in bold type.

occur

1. Acceleration occurs when thrust is greater than drag.

2. Vibration of aircraft due to landing tends to occur mainly at the lower frequencies.

3. The heaviest of all the naturally occurring atoms is uranium. It occurs in three isotopic forms.

estimate

4. It is the purpose of this chapter to estimate the danger arising from uranium radiation.

5. Measurements of the changes of the Sputnik's orbit allowed the scientists to estimate the air density at a height of 200 kilometers.

6. The inside temperature of the Sun is estimated to be about 30,000,000° C.

reveal

7. Maxwell's equation reveals that all the waves of the spectrum have the same velocity in vacuum.

8. Radar is most successful in revealing isolated objects.

9. The length of the new turbojet is about 150 ft. Precise dimensions have not yet been revealed.

VII. Translate the sentences paying attention to the meanings of the noun “background”.

1. The best time for the observation of Sputniks is when the Sun is below the horizon and illuminates the Sputnik against a dark background.

2. The book describes the background of current work on rockets and guided missiles.

3. The last four chapters of the book give the student background and related information which will broaden his understanding of the gas-turbine engine field.

4. One needs a background in astronomy and astrophysics in order to fully understand this text.

5. Every mechanic must have a background of special technical knowledge in order to operate and inspect his apparatus.

VIII. Translate the sentences paying attention to the meanings of  “in respect to” and “with respect to”.

1. Titanium metal is midway between steel and aluminum alloy in respect to mechanical strength and temperature resistance.

2. With respect to range surface-to-surface missiles may be of two types.

3. With respect to solar particles it is of course possible to say that they penetrate an interplanetary gaseous plasma made up by the particles constituting the slower components of solar corpuscular radiation.

4. Gamma rays and X-rays are both forms of electromagnetic radiation and differ only with respect to origin.

5. In unpowered flight in space the principal control problem is that of controlling the orientation of the vehicle with respect to a specified reference system.    

IX. Translate the sentences paying attention to the adjectives in bold type.

1. An inner wing is that part of a long airplane wing that lies inside the outer wing.

2. The upper part of the earth's atmosphere is called the ionosphere.

3. In a good conductor like copper, some of the outermost orbital electrons are only slightly bound to the atomic nucleus.

4. The uppermost part of the atmosphere, called the ionosphere, is located above the stratosphere.

5. The innermost planet of the solar system is Mercury.

X. Translate the sentences paying attention to the meanings of the verb “to draw”.

1. Like the piston engine, gas turbine draws in atmospheric air which is compressed and then heated.

2. At saturation, electrons are being drawn to the anode as fast as the filament can produce them.

3. In Fig. 81 the lines showing the direction of the pressure are drawn at right angles to the surface of the airfoil.

4. History's first flight in outer space has made it possible to draw the immensely important scientific conclusion that manned flights in space are possible.

5. Above the critical temperature there is no reason to draw any distinction between liquid and vapour.

TEXT 18 B

Communicating Through the Earth

Try to understand what the text is about by its title:

1. How do we communicate with people beyond the horizon? What can be made to follow the curve of earth's surface?

2. Of course, we can send electrical signals through wires around any curves. In the Nineteenth Century, copper wires were strung across the continents and ocean floors and the world was united through telegraphy. That takes a lot of copper, though, and a lot of maintenance.

3. We could send light-wave signals and do away with wires, but light waves move in a straight line and won't curve around the earth's bulge. We would have to set up relay stations or place mirrors in orbit to make that work.

4. Radio waves, like light waves but a million times longer, do better. They travel in straight lines, too, but the upper atmosphere contains regions rich in charged particles (the ionosphere) that tend to reflect the radio waves. It is as though there were natural mirrors in the sky. That makes it possible to send radio signals long distances, and in the Twentieth Century the world was united without wires.

5. However, the ionosphere is affected by the solar wind. When the sun produces flares, an electrical storm can take place that will disrupt radio communications.

6. But short radio waves (microwaves) can go right through the ionosphere and be amplified and sent on by communications satellites. As communications satellites improve, signals will be sent from place to place on earth with so little trouble that it would seem unreasonable to ask for anything better.

7. What can go through the earth itself? Light certainly can't. Radio waves can't. We can't even string wires through the earth to carry electrical signals.

8. One thing that does travel through the body of the earth is an earthquake wave, but it takes a very hard blow to set the earth to vibrating perceptibly.

9. On the other hand, certain massless subatomic particles called neutrinos travel at the speed of light and go through matter as though it weren't there. A beam of neutrinos could travel through trillions of miles of solid lead and come out the other end just about unaffected. Neutrinos reach us from every direction and almost every neutrino that does so passes right through the earth in less than a 20th of a second (and through us if we are in their paths).

10. This doesn't mean that neutrinos can't be detected. Out of many trillions, one neutrino may occasionally combine with an atomic nucleus and induce a detectable change.

11. Thus, huge vats of cleaning fluid made up of molecules that include chlorine atoms can serve as a "neutrino telescope". Such neutrino telescopes can be placed in mines, a couple of miles under the earth’s crust. In that case, nothing can reach them but neutrinos, and, in this way, neutrino-producing reactions deep in the sun's core can be studied.

12. Scientists can produce neutrino beams without much trouble. Some day it might be possible to send them out in Morse code or in more complicated modulation. The day may come when improved neutrino telescopes, using water rather than cleaning fluid, will be placed all over the earth. Eventually television sets might be built that would incorporate the equivalent of neutrino telescope and convert the signals directly into sight and sound.

13. If this could be done, communications satellites would be unnecessary and so would relay stations of any sort. Any two points on earth's surface (or in mines, or under the sea) would be connected by a mathematically straight line along which neutrinos would move at the speed of light. There is no way of communicating more quickly.

14. For that matter, neutrinos move in a straight line throughout the universe. They are unaffected by the electromagnetic fields and dust clouds that can disrupt or block microwaves and light.

15. In the end, then, it may be that communications among worlds would be carried out through neutrino beams.

16. Perhaps that is why we aren't detecting signals from other intelligent civilizations out there. We're looking for beams of  microwaves, but perhaps we should be looking for beams of neutrinos.


 

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