Российской Федерации Федеральное агентство по образованию

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Тип	Учебное пособие

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Exercise 3. Translate the following sentences paying special attention to different meanings of “that” and “those”.

The distinguishing feature of a converging lens is that it is thicker at the center than at the edge.
We know that the telescope is an instrument that presents to the eye an enlarged image of distant objects.
A field of view afforded by a plane mirror is very similar to that of a simple window.
There are close analogies between the effects produced by a thin lens and those produced by a single spherical refracting surface.
That spherical aberration can be completely eliminated for a single lens by aspherising is a very important fact in optical design.
The diaphragm restricts the rays to those which pass through the central portion of the lens.

Exercise 4. Put the verbs in brackets into the correct form.

Light (to travel) faster in empty space and (to slow) down upon entering matter.
Optics (to progress) rapidly by the early years of the 19^th century.
Since 1940 there (to be) a great resurgence in optics on the basis of information and communication theory.
If space (to be) empty, light (to travel) faster.
In 1841 Gauss (to publish) his classical book on geometrical optics, in which he (to expound) the concept of the focal length.
Before More Hall (to find) the correct combination of flint and crown lenses he (to experiment) with different types of glass.
The scientist (to invent) the form of the refracting telescope, which (to be) the basis for modern refractors.
How (to work) a transmitter?

REVIEW OF THE CHAPTER I

Exercise 1. Give a brief summary of the texts.

Define the main problems dealt with in the texts. Try to use the following words and expressions in your summary: the article covers the period (periods), special attention is given to, thus, hence, that’s why.
Exercise 2. Topics for discussion on the material of Chapter I.

Who contributed much to the development of geometrical optics?
In your opinion, what types of camera will be the most popular in future and why?

SUPPLEMENTARY TASKS

IMPROVE YOUR TRANSLATION PRACTICE

TASK 1

Translate the text and discuss the topics given below.
The History of the Telescope

At least two other Dutch spectacle makers made telescopes about the same time, and there were rumours of some such sort of magical device during the 16^th century. Nevertheless, a Dutch eyeglass maker, Hans Lippershey, has been given credit for the invention of the telescope in 1608; when he offered it to the government for military use, they required that it be converted to binocular form. Lippershey was the first to describe the telescope in writing.

By 1610, Galileo announced the telescopic observations of the moon and planets, which signaled the end of the Ptolemaic theory of the heliocentric solar system. Galileo’s telescope was a simple refractor, employing two lenses in a tube. In 1609 Galileo learned of the invention of the telescope, a three-power instrument, which he quickly improved to eight, twenty and then thirty power. These were the most powerful instruments of his time and with them he made the discoveries that established Copernican system.

Keppler invented the form of the refracting telescope, which is the basis for modern refractors; it has a convex lens placed in back of the focus. The reflecting telescope invented by Isaac Newton used an on-axis planar mirror to move the focus of the parabolic reflector to a point outside the light collecting cylinder; reflector telescopes avoid the problem of lens chromatic aberration, which affect refractors. Variations of the Newtonian reflector, in which the light was reflected back through a hole in the primary mirror, were invented by James Gregory in 1663 and by Cassegrain in 1672.

One hundred years later, Jesse Ramsden, an English instrument maker who rose from poverty to membership in the Royal Society, discovered that the Cassegrain design may be used to reduce spherical aberration using a paraboloidal reflector and a hyperboloid for the secondary reflector. Microwave reflector antennas often employ the Cassegrain design, with the feed-horn between the primary and secondary reflectors. A lens design, which resolved the problem of chromatic aberration for refractor telescope was discovered in 1733 by Hall but kept secret until it was uncovered and used commercially in 1759 by John Dolland and his son.

A third type of telescope, which uses a spherical mirror and a correcting lens was invented in 1930 by Bernhard Schmidt. It employs a correcting plate at the telescope aperture to compensate for spherical aberration, thus it is a combination reflector-refractor system. The Schmidt telescope serves astronomy as a wide-angle camera. The Schmidt-Cassegrain telescope is the most popular among amateur astronomers because of its compact design and large aperture and because the optics are completely enclosed.

Exercise 1. Rearrange the sentences in the chronological order.

Keppler invented the form of the refracting telescope, which has a convex lens placed in back of the focus.
Hans Lippershey has been given credit for the invention of the telescope in 1608.
In 1930 Bernhard Schmidt invented a third type of telescope, which uses a spherical mirror and a correcting lens.
In 1609 Galileo learned of the invention of the telescope, built a three-power instrument.
Jesse Ramsden, an English instrument maker, reduced spherical aberration in the Cassegrain design, having used a paraboloidal reflector and a hyperboloid for the secondary reflector.

Exercise 2. Topics for discussion.

The invention of the telescope was a great step in science.

Galileo and Keppler much contributed to telescope-making.
Why are there different types of telescopes?

TASK 2

Translate the text without a dictionary using terms given below. Pay special attention to the underlined sentences.
Holography

The use of a lens to image an object is one of the oldest principles in optics and photography. However, in 1948 Gabor introduced a two-step imaging process in which an intermediate record, containing the information necessary to create an image, is formed.

The 2-step imaging process consists of first photographing the interference pattern which exists when a diffracted or object field is allowed to interfere with a reference field or background wave (usually a plane or spherical wave) on or off axis with respect to the diffracted field. The 1-st step is called the formation or recording, The 2-nd step, called the reconstruction, consists of placing the photographic transparency (film) into a coherent beam of light and producing an image of the original object.

The resulting record of the interference pattern obtained in the 1-st step is called a hologram after the Greek word "holos", which means "the whole", because the photographic record contains information concerning both the amplitude and phase of the original object.

The hologram bears little resemblance to the object, and upon visual observation contains a seemingly meaningless combination of fringes or diffraction patterns. The image of the object which is obtained from a hologram is referred to as the reconstructed image, and there are two types. A real image is one that appears on the opposite side of the hologram from the source and has the property that no auxiliary focusing devices are needed to record a focused image. A virtual image is one that appears on the same side of the hologram as the source and has the property that an additional focusing device is needed to detect a focused image.

The entire process is known as the hologram process and the wave-front reconstruction process, and also the science of holography.

background wave – опорная волна

coherent beam of light – когерентный пучок света

diffracted or object field – дифрагированное поле или поле предметной волны

fringes or diffracted pattern – полосы или дифракционная картина

interference pattern – интерферограмма, интерференционная картина

intermediate record – промежуточная запись

photographic transparency – фотографическая пленка

plane or spherical wave – плоская или сферическая волна

reference field – опорное поле

two step imaging process – двухшаговый процесс формирования изображения

wave-front reconstruction process – процесс восстановления волнового фронта

Exercise 1. Retell the text, find out three main ideas.
Exercise 2. Read and translate two definitions of the word “hologram”.

1. Hologram is a pattern produced by the interference between one part of a split beam of coherent light, e.g. from a laser, and the other part of the same beam reflected off an object.

2. Hologram is a photographic reproduction of a pattern that when suitably illuminated produces a three-dimensional picture.

TASK 3

Read the text paying attention to the specifications of the optical instruments and the ways they are used.

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