3. Match the words and their definitions:

Conductor, insulator, resistance, accumulate, radiation, convert

1. collect or gather over a period of time;

2. the power of a substance to prevent passing through it of an electric current;

3. an object which does not allow electricity to pass through it;

4. something that acts as a path for electricity, heat;

5. change into another form, substance or state

6. energy that comes from a particular source

4. Find synonyms to the words using the text:

To vary, opportunity, to be used, to transform, to get, to collect, media, half-conductor.

5. True or false. If the statement is false, correct it.

1. Semiconductor is a material whose conductivity ranges between non-conductors and insulators.

2. They are great variety of elements, chemical compounds, minerals.

3. Conductivity of semiconductors increases with cooling and decreases with heating.

4. Semiconductors do not react to light and radiation.

5. The electricity generated by semiconductors can produce heat but not cold.

6. Name the main properties of semiconductors and tell the class how they are used in electronics.

7. a). Translate the sentences into Ukrainian:

1. The conductivity of metals is very little influenced by temperature.

2. Photoresistance is widely applied for reproducing sound in cinematography.

3. Semiconductors could solve complicated engineering problems.

b). Translate the sentences into English:

1. За допомогою напівпровідників можливо перетворювати тепло в електроенергію.

2. Напівпровідники можуть виробляти не тільки тепло, але й холод.

3. Напівпровідникові матеріали можуть підтримувати постійну температуру, незалежно від температурних змін навколо.

TEXT B

1. Read and translate the text in a written form: Bell Telephone Laboratories

Bell put the transistor into production at Western Electric in Allentown, Pennsylvania. They also licensed it to a number of other electronics companies, including Texas Instruments, who produced a limited run of transistor radios as a sales tool. Another company liked the idea and also decided to take out a license, introducing its own radio under the brand name Sony. Early transistors were "unstable" and only suitable for low-power, low-frequency applications, but as transistor design developed, these problems were slowly overcome. Over the next two decades, transistors gradually replaced the earlier vacuum tubes in most applications and later made possible many new devices such as integrated circuits and personal computers. Shockley, Bardeen and Brattain were honored with the Nobel Prize in Physics "for their researches on semiconductors and their discovery of the transistor effect". Bardeen would go on to win a second Nobel in physics, one of only two people to receive more than one in the same discipline, for his work on the exploration of superconductivity.

In August 1948 German physicists Herbert F. Mataré (1912– ) and Heinrich Walker (ca. 1912–1981), working at Compagnie des Freins et Signaux Westinghouse in Paris, France applied for a patent on an amplifier based on the minority carrier injection process which they called the "transistron." Since Bell Labs did not make a public announcement of the transistor until June 1948, the transistron was considered to be independently developed. Mataré had first observed transconductance effects during the manufacture of germanium duodiodes for German radar equipment during WWII. Transistrons were commercially manufactured for the French telephone company and military, and in 1953 a solid-state.

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

TEXT C

1. Mind the following words:

tremendously – дуже сильно

to prevent – перешкоджати

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

3. Answer the following questions:

1. What is semiconductive material?

2. Can it vary its properties?

3. What material is used to create semiconductors?

4. What devices have semiconductor technology in common?

5. What is the difference between conductors and insulators?

UNIT 8

TEXT A

Radar

1. Read and remember the following:

1. Determine-визначати

2. radar set- радарна установка

3. transmitter- передавач

4. receiver-приймач

5. power supply-джерело живлення

6. frequency-частота

7. beam-промінь

8. velocity-швидкість

9. accuracy-точність

10. elevation-висота

11. rotate-обертатись

12. three-dimensional-трьохвимірний

2. Make up sentences using the words from ex1.

3. Read and translate the text:

The word “radar” means Radio Determination and Ranging. Radar equipment is capable of determining by radio echoes the presence of objects, range and recognizing their character.

There are several types of radar sets, all of them consisting of six essential components, namely: a transmitter, a receiver, an antenna system, an indicator(s), a timer, and of course, a power supply.

A radar set detects objects by sending out short powerful pulses of ultrahigh frequency radio wave energy from a high power transmitter. The directional antenna takes this energy from the transmitter and radiates it in a beam (similar to that of a searchlight).

As the transmitted energy strikes an object, a portion of it is reflected back. The receiver picks up the returning echo through its antenna and translates it into visual readable signals on a fluorescent screen. The appearance of these signals shows the presence of an object within the field of view of radar.

The electron beam sweeps across the fluorescent screen in somewhat the same way as a hand sweeps across the face of a clock. Just as a hand of a clock completes its sweep in sixty seconds, the electron beam can be made to travel across any desired portion of the screen in some predetermined interval of time. It is the timer, which is the synchronizer of the whole system that times the transmitter pulse and the indicator. The use of these timed pulses and the fact that the radio waves travel at the constant velocity of light gives a simple means of measuring range. The accuracy with which time is measured determines the accuracy of the range.

How then is the direction in which the object lies to be found? Both azimuth and elevation can be determined by means of the directional antenna. The antenna may be rotated as the pulses are sent out and the strongest signal appears on the screen when the antenna points directly at the object. The direction of the antenna enables the determination of azimuth and elevation. Thus, with the help of a radar set we can get three-dimensional location of an object.

The wide use of radar sets in our everyday life will make air and sea entirely safe. Radar may be installed on every ship at sea as well as in every large harbour. They will prevent collisions in fog and aid a ship to sail safely into any harbour, regardless of night or weather. Similarly airplanes will be able to fly over mountain ranges in storms and affect blind landing during poor visibility.

4. Answer the questions to the text:

1. What does the word “radar” mean?

2. What is radar used for?

3. What does the set consist of?

4. What unit of a radar set sends signals to detect an object?

5. What part picks up a back signal?

6. When is an object considered to be found?

7. What component points directly to a found object?

5. Match the words that go together:

1. radar a). sweep

2. transmitter b). rotate

3. receiver c). screen

4. antenna d). send a signal

5. electron beam e). determine

6. measuring f). range

7. fluorescent g). pick up

6. Make up an algorithm how a radar set detects an object.

7. Translate into Ukrainian:

1. Radar equipment is capable of determining objects, range and their character.

2. The directional antenna takes the energy from the transmitter and radiates it in a beam.

3. If the object is found, a portion of sent energy is reflected back.

4. The accuracy with which time is measured means the accuracy of the range.

8. Translate into English:

1.Існує декілька типів радарних установок, але всі вони мають 6 основних складових.

2.Радар знаходить об’єкти посилаючи короткі сигнали високої частоти через передавач.

3. Електронний промінь обертається на екрані зазначений час.

4. Коли на екрані з’являється найсильніший сигнал, антенна точно вказує напрямок об’єкту.

TEXT B

1. Read and translate the text in a written form:

Radar

Electromagnetic waves reflect (scatter) from any large change in the dielectric or diamagnetic constants. This means that a solid object in air or vacuum, or other significant change in atomic density between the object and what’s surrounding it, will usually scatter radar (radio) waves. This is particularly true for electrically conductive materials, such as metal and carbon fiber, making radar particularly well suited to the detection of aircraft and ships. Radar absorbing material, containing resistive and sometimes magnetic substances, is used on military vehicles to reduce radar reflection. This is the radio equivalent of painting something a dark colour.

Radar waves scatter in a variety of ways depending on the size (wavelength) of the radio wave and the shape of the target. If the wavelength is much shorter than the target’s size, the wave will bounce off in a way similar to the way light is reflected by a mirror. If the wavelength is much longer than the size of the target, the target is polarized (positive and negative charges are separated), like a dipole antenna. When the two length scales are comparable, there may be resonances. Early radars used very long wavelengths that were larger than the targets and received a vague signal, whereas some modern systems use shorter wavelengths (a few centimetres or shorter) that can image objects as small as a loaf of bread.

Short radio waves reflect from curves and corners, in a way similar to glint from a rounded piece of glass. The most reflective targets for short wavelengths have 90° angles between the reflective surfaces. A structure consisting of three flat surfaces meeting at a single corner, like the corner on a box, will always reflect waves entering its opening directly back at the source. These so-called corner reflectors are commonly used as radar reflectors to make otherwise difficult-to-detect objects easier to detect, and are often found on boats in order to improve their detection in a rescue situation and to reduce collisions. For similar reasons, objects attempting to avoid detection will angle their surfaces in a way to eliminate inside corners and avoid surfaces and edges perpendicular to likely detection directions, which leads to “odd” looking stealth aircraft. These precautions do not completely eliminate reflection because of diffraction, especially at longer wavelengths. Half wavelength long wires or strips of conducting material, such as chaff, are very reflective but do not direct the scattered energy back toward the source. The extent to which an object reflects or scatters radio waves is called its radar cross section.