8. True (t) or false (f) sentences. Correct the false ones.

1. The word ‘supersonic’ means slower than light.

2. Nature has a much less range of sounds than people do.

3. Supersonic waves can generate different materials at a great depth.

4. The faults of different materials reflect supersonic waves.

5. Supersonic apparatus measure the thickness of different objects with great inaccuracy.

6. Supersonic waves are very sensible.

7. The principle of supersonic waves forms the basis of a method of cleaning dirty air.

8. Supersonic waves can break up and crash various substances.

9. Supersonic waves are able to bore holes.

10. Supersonic waves never change their speed.

9. Answer the following questions about the text.

1. What are supersonic waves?

2. How do supersonic waves travel?

3. Supersonic waves are able to penetrate different materials, aren’t they? Why is it so important?

4. What else can supersonic waves do?

5. Where can supersonic waves be applied?

6. When were supersonic waves discovered?

10. Translate into English.

1. Надзвукові хвилі використовуються у різних сферах життя людини.

2. Такі хвилі мають здатність проникати в різні матеріали.

3. Надзвукові хвилі утворюються вібраціями певної частоти.

4. Людське вухо здатне вловлювати лише невелику кількість вібрацій.

5. Поняття “надзвуковий” означає рух скоріший за швидкість звуку.

TEXT B

1.Read and translate the text in a written form: What Makes Radio Waves?

Radio waves are usually produced by electric current alternating at radio frequency flowing in a special purpose conductor, called an antenna. Antenna dimensions must generally be comparable to wavelength to work efficiently. Very long waves are not practical because of the enormous antennas needed to produce them, although they are sometimes produced by lightning. Radio waves are also produced by cosmic phenomena in deep space. Actually, any kind of reciprocating motion of electric charges or magnets can produce radio waves if it is fast enough. Although very impractical, even a person waving a charged stick very fast can produce faint radio waves.

Propagation is a term that describes the travel of electromagnetic waves, there being three main modes of propagation. The first is a straight line travel: the manner that radio waves travel through deep space (ignoring the slight deviations caused by gravity under the theory of relativity). A second way is skip, which is bouncing between the surface of the earth and the ionosphere. Frequencies between 3 MHz and 30 MHz are most reliable for this kind of propagation, called High Frequency. The third way is to hug the surface of the earth as it curves around. Radio waves of very low frequency most often travel this way.

Radio signals can also enter two ionospheric layers of differing electron densities and duct between them. The image at the right illustrates this. Two radio signals of differing elevation angles are broadcast into the ionosphere, where they split into ordinary (red) and extraordinary (green) components. In this example, the ordinary component began ducting between the E and F ionospheric regions.

Although this mode of radio wave propagation is less common than the skip mode, it is nonetheless an important mode because it permits radio signals to travel significant distances with little attenuation.

Radio waves were first predicted by mathematical work done in 1865 by James Clerk Maxwell. Maxwell noticed wave-like properties of light and similarities in electrical and magnetic observations and proposed equations that described light waves and radio waves as waves of electromagnetism that travel in space. In 1887 Heinrich Hertz demonstrated the reality of Maxwell’s electromagnetic waves by experimentally generating radio waves in his laboratory. Many inventions followed making practical use of radio waves to transfer information through space.

2. Make up a plan of the text in the form of questions.

TEXT C

1. Mind the following words:

oscillate –коливатись

ham radio – аматорське радіо

charged particles – заряджені частки

2. Listen to the text “Radio Waves” and try to understand it.

3. Answer the following questions:

1. What are radio waves?

2. What wavelength does a radio wave have?

3. What are radio waves used for?

4. Can they pass through Earth’s atmosphere?

5. What can happen with them in the ionosphere?

UNIT10

TEXT A

Radio Transmitters

1. Read and memorize the following words and word-combinations and their translations.