READ AND LEARN THE MORSE CODE

The telegraph is a modern method used for rapid communication. Each tetter of the alphabet is coded into dots and dashes. There are intervals between the coded letters and longer intervals between the coded words. The code in common use is called the Morse code after the name of its inventor.

THE MORSE INSTRUMENT

The Morse instrument consists essentially of an electro­magnet which, when a current passes through its coils, draws down an armature for a short or a long time. It may be arranged either as a "sounder", in which case the operator who is receiving the message listens to the clicks and notices whether the intervals between them are long or short; or it may be arranged as a 'printer' to print dots and dashes upon a strip of paper drawn by clockwork through the instrument. If the Morse instrument is arranged for printing, the attraction of the armature downwards lifts a small inky wheel and pushes it against a ribbon of paper. If the current is momentary the wheel prints a dot. If the current continues to flow for a longer time the ribbon of paper moves on and the ink-wheel marks a dash.

The Morse code, or alphabet of dots and dashes, is as follows:

A .__ J . __ __ __ S . . .

B __ . . . K __ . __ T __

C __ . __ L __ . __ U . . __

D __ . . M __ __ V . . . __

Е . N __ . W . __ __

F . . __ . О __ __ __ X __ . . __

G __ __ . P . __ __ . Y __ . __ __

H . . . . Q __ __ . __ Z __ __ .

I . . R . __ .

Full stop .. .. ..

Repetition .. __ __ ..

Hyphen — ..—
Apostrophe __ __ __ __

Задание 14

Прочтите и переведите текст: TEXT

WAVE MOTION

One of the most important phenomena in nature is the transmission of energy from one point to another by wave motion. When you drop a stone into a pool of still water, the surface of the water is soon covered with circular waves. The water does not really move from the central point but it rises and falls again. Motions of this kind are wave motion.

We can see water waves almost every day. We make use of light waves to see the water waves and we hear sounds by means of sound waves. All wave motions possess three characteristics:

1) amplitude, which is the height or strength of the wave;

2) frequency, the number of waves per second; and 3) wavelength, the distance from the crest of one wave to the crest of the next. Sound waves are produced by vibrations. Sound waves travel through the air at a speed of about 1,100 ft. per second.

The microphone, the loudspeaker and headphones are devices used in transmitting sound (Fig. 15).

To find the velocity (or the speed) of the wave motion we multiply the frequency by the avelength:

ν = fl

where f stands for frequency ['fri :kwənsi],

l stands for wavelength ['weivləηө],

v stands for velocity [vi'lositi].

This important equation is true for electric waves as well as for sound waves.

Radio waves are electric waves of very high frequency; they travel through space with the speed of light. They differ from other wave forms, such as light waves, heat waves or X-rays, only in frequency (number of vibrations per second).

Figure 17 shows waves being sent out in all directions from a transmitting an­tenna.

УПРАЖНЕНИЯ

I. Выпишите из текста интернационализмы.

II.Ответьте на вопросы:

1. What is one of the most important phenomena in nature? 2. When can you see water waves? 3. What waves are there in nature? 4. How can you hear sounds? 5. What are the main characteristics of waves? 6. What is amplitude? 7. What is frequency? 8. What is wavelength? 9. What formula do we use to find the velocity? 10. What do the letters f, l; and v stand for? 11. What is the velocity of light?

III. Образуйте производные от слов:

transmit, cover, circus, speak, vibrate, frequent, equal, differ, move

IV. Выполните задание:

1. Describe the experiment demonstrating sound trans­mission (A bell ringing in a vacuum cannot be heard).

Use the following words and expressions:

to transmit sound by air, gas (or any material medium), to place a bell in an evacuated jar, to remove the air from, with the help of a vacuum, the ringing of the bell, to become fainter, to hear something

2. Translate into Russian the description of the experiment:

As soon as the air is ad mitted, however, the ringing becomes clearly audible again. The vibrating bell strikes air molecules, knocking them away from the metal surface. These fast moving molecules strike the adjacent air molecules and they in turn strike others. Upon reaching the side of the jar, the glass walls are periodically bombarded by the molecules and set vibrating. The walls in turn set the outside air vibrating. Arriving at the observer's ear, the disturbance strikes the eardrum, setting it into motion. Without air to transmit the vibrations from the bell to the inside surface of the glass jar, no sound could ever leave the jar.

Задание 15