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The Past and the Future of the Laser 8 глава
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In many ways, the laser was a solution looking for a problem. Well, the problems soon followed in great numbers. It would be hard to imagine the modern world without lasers. They are used in everything from CD players to laser printers, fibre-optics and free-space communications, industrial cutting and welding, medical and surgical treatment, holography and light shows, basic scientific investigations in dozens of fields, including Star Wars weapons research. The unique characteristics of laser light make these and numerous other applications possible. In fact, it is safe to say that the vast majority of laser applications have not yet even been suggested.
However, if treated inadequately, an extremely powerful beam of laser light can be a source of destruction. You must never stand in the way of the cutting laser beam. Only by looking directly into the beam or its reflection from a shiny object you can damage your eyes. Besides, laser power supply being typically 2500 V or more, a QUALIFIED person must provide external power supply, as ordinary insulation is not enough. Thus, no matter how advantageous and useful they are, lasers are dangerous. Hence, safety rules must be strictly observed.
IV. Provide detailed answers to these questions.
1. What is a laser? What other sources of light do you know?
2. What was the first laser like?
3. Does the laser possess any unusual properties? What are they?
4. When did the laser age begin?
5. Many substances produce laser light, don't they?
6. Were there any surprising discoveries?
7. Why is it difficult to imagine our life without lasers?
8. What are the most common uses of lasers?
9. Why are lasers considered dangerous?
V. Explain what the author means by the following statements.
1. A laser is a source of light but unlike anything that had ever been
seen before 1960.
2. With this invention the laser age was born.
3. According to this legend, they are supposed to work fairly well.
4. In many ways, the laser was a solution looking for a problem.
5. In fact, it is safe to say that the vast majority of laser applications
have not yet even been suggested.
6. If treated inadequately, an extremely powerful beam of laser light
can be a source of destruction.
VI. Complete the gaps with suitable words from the box.
| wavelength destruction applications safety liquids intense powerful features coherence semiconductor |
A laser is a source of monochromatic, directional and coherent light. Monochromicity means light of the same... or colour. Light waves travelling precisely in step explain the property of.... Besides, the laser beam can be easily manipulated. These unusual... make laser light unique. The first laser consisted of a specially prepared synthetic ruby rod and a... flash lamp. During the experiment the researches observed an... pulse of red light. Later solid-state materials, gases,... and... crystals were recorded having laser qualities. Lasers are considered to be a multibillion-dollar industry having numerous... such as cutting and welding. However, lasers can be the source of both construction and.... That is why... rules must be strictly observed.
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VII. You have visited a very interesting exhibition on the applications of
lasers. Your friend could not go with you and now he is interested in
everything you saw or heard. Share your impressions with him and
persuade him to visit this exhibition.
You can start like this: - Hello, Peter. I hear you have visited a laser
exhibition. Is that true?
- Certainly! And I must say it was worth visiting....
VIII. What information have you received from your friend? Would you
like to visit this exhibition? What do you expect to see there?
Further Reading
I. Practise reading these words.
oscillator [,os['leit3] behaviour [bi'heivja]
excited [ik'saitid] via [vaia]
spontaneous [spDn'temjas]
II. Match the English words and expressions with their Russian
equivalents.
1. light amplification а) усилитель
2. spontaneous emission b) вынужденное излучение
3. stimulated emission с) излучение; радиация; испускание
4. radiation d) спонтанное излучение
5. oscillator e) усиление света
6. amplifier f) возбужденная частица
7. ground state g) генератор
8. population inversion h) высший энергетический уровень
9. excited particle i) основное (квантовое) состояние
10. upper energy level j) инверсия заселённости (энергети-
ческих уровней)
III. Do you remember what the word 'laser' means? Read the text and
learn how lasers work.
How Lasers Work
The word 'laser' is an acronym standing for light amplification by stimulated emission of radiation. This is not exactly so since most lasers are actually oscillators (generators or sources of light) and not
amplifiers (devices for increasing the strength of asignal), though such lasers are also possible and used for some applications. However, nearly all lasers have the following in common:
A lasing medium. This can be a solid, liquid, gas, or semiconductor material, which can be pumped to a higher energy state.
A means of pumping energy into the lasing medium can be: optical, electrical, mechanical, chemical, etc.
A resonator consisting of a cavity with a pair of mirrors (flat or concave), one at each end of the laser for making stimulated light bounce back and forth through the lasing medium. One of the mirrors is totally reflective, the other being partially transparent to allow the laser beam to escape.
Lasers are based on a simple principle of atomic behaviour. Normally, nearly all atoms, ions, or molecules (depending on the particular laser) of the lasing medium are at their lowest energy level or 'ground state' (1). To produce laser action, the energy-pumping device must achieve population inversion through driving the majority of
Basic Laser Operation
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particles to the upper energy level (2). Sometimes dropping to the 'ground state' the excited particle emits a single photon of light. This is called 'spontaneous emission', not exactly useful, although causing the glow of a neon sign or the phosphor coating of a fluorescent lamp (3). Yet Einstein showed that a photon emitted nearly parallel to the direction of the resonator (3,4) will bounce back and forth many times stimulating excited particles along the way to lose the photons possessing three exactly the same qualities: wavelength, phase and direction. The tendency progresses resulting in the photons flow increasing via this 'stimulated emission' process (5). The resulting beam can be pulsed or continuous; visible, infrared or ultraviolet; less than a milliwatt - or millions of watts of power. It has the unique properties of being highly monochromatic, coherent and easily manipulated - something impossible with more common light sources. There you have it! Everything else is just details.
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IV. Explain the meaning of these words and expressions.
laser, oscillator, amplifier, photon, 'ground state', 'spontaneous emission', 'stimulated emission'
V. Give detailed answers to these questions.
1. Why is the acronym 'laser' not very exact?
2. Do lasers have a common structure?
3. What lies in the basis of laser operation?
4. The lasing medium consists of various particles, doesn't it?
5. What are the stages of emission?
6. In what condition are the particles found normally?
7. Why is it necessary to move the particles to the upper energy level?
8. When do excited particles lose photons?
9. How does the massive flow of photons begin?
10. What is the output of the laser?
VI. What does the laser consist of? Complete the table with the data from
the text.
| Laser Part | Function |
| … | … |
VII. You are at the Great Laser Show with your friends. One of them gets interested in how lasers work. What basic information will you give him?
Activity
I. Your friend is not attentive at the lesson and has understood nothing
about lasers. At the end of the lesson the teacher suddenly gives a test.
Your friend has some questions about laser structure and operation.
Help him to pass the test.
II. Discussion. Lasers are certainly part of our life. However, like many
other things they are not perfect. What are advantages and
disadvantages of lasers? Do you think all laser technologies should be
developed? What are the potential dangers of lasers?
III. Solve the crossword.
Across:
1. it is measured with the help of a laser
Down:
2. substances can be gassy, liquid and...
3. part of a resonator
4. if the supply of energy is not maintained,
the laser beam becomes...
5. an atom / ion / molecule
6. a generator or a source of light
7. opposite to 'flat'
8. it is necessary to... a particle in order to
make it lose a photon
9. the function of a mirror is to... objects
Writing
I. Write two paragraphs, one about advantages, the other about possible
dangers of lasers.
II. Translate the following passage into Russian. Use the dictionary if
necessary.
Lasers in Art and Entertainment
Lasers make impressive visual effects possible. In light shows it is common to use lasers emitting few laser wavelengths. Prisms are used for separating each colour. This results in producing many laser beams of different colours. The application of small vibrating
mirrors controlled by a computer provides the possibility of moving each laser beam very rapidly thus creating moving coloured images. Since our vision is based on seeing the image a little time after it has disappeared, we are capable of observing a full picture created by a laser beam in spite of its being illuminated in each point for a very brief period of time. The first devices were used for making two-dimensional moving pictures on screens, but the latest developments are designed with the view of producing three-dimensional moving sculptures in free space - an impossible task to be performed by other means. Without the laser, the unique three-dimensional imaging properties of holography would not exist.
Section B. Industrial Gases
Lead-in
I. Discuss the following questions.
a) How do we depend on gases? What gases do you know?
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b) What is air pollution? What are the causes and possible
consequences of air pollution?
II. Listen to the conversation and say what you have learnt about
the industrial gases.
Teacher: Pavel! Where are Nick and Olga?
Pavel: I'm afraid they are late.
Teacher: I insist on both of them coming on time. We can't work like
this.
Pavel: And what are we going to do today, I wonder?
Teacher: We'll speak about some industrial gases and their
properties.
Pavel: And what are industrial gases?
Teacher: Well, these gases are used in industry in making various
products.
Pavel: Are these gases natural?
Teacher: Well, some of them, such as oxygen, nitrogen etc. are found in free state in the air. Others are man-made, like freon, which is used in welding.
Pavel: I suppose they have a very wide range of applications.
Teacher: You are quite right. The importance of using them can hardly be overestimated. However, gases are not only part of the industrial process. They also pollute the environment. Do you know what problems air pollution causes?
Pavel: Certainly. I've heard a lot about acid rains, the greenhouse effect, the ozone layer depletion.
Teacher: Very good. Well, Nick, here you are at last.
Nick: Sorry for being late, sir.
III. Complete the dialogues.
a)-Olga,...?
- It's past 12, sir. I'm sorry for...
- It's OK, but I insist on...
- …
b) -..., I'd like to know?
-First, I'm going to tell you...
- It sounds interesting. Are they used for....?
- …
c) - Do industrial gases pollute the environment?
- …
- What problems...?
- Well, the hottest problems are...
IV. Match a line in A with a line in B.
А В
1. I'm sorry for being late. a) It results in destructing the
2.I insist on your coming on biological balance of the
time. soils and water (eutro-
3. Scientists object to chloro- phication).
fluorocarbons being used in b) They have serious reasons.
industry. c) I hear of natural pollutants
4. Where is helium used? being sent into the atmos-
5. Are all pollutants man-made? phere for billions of years.
6. How does the excess of d) Sorry, sir.
nitrogen in the air influence e) In arc welding.
the ecosystems? f) It's OK.
Language Practice
Vocabulary
I. Match the words with the opposite meaning.
the same to clean
natural non-flammable
colourful man-made
flammable abundant
toxic dioxide
to pollute non-toxic
monoxide colourless
rare different
II. Make all possible word combinations.
industrial rain
natural effect
solar gases
combustible state
air radiation
fossil pollution
acid pollutants
greenhouse fuels
III. Find in each line the derivative from the first word.
1. perform - performance, form, super, robot
2. exact - object, extra, exactly, react
3. object - inject, subject, objection, substance
4. danger - development, average, discovery, dangerous
5. experience - science, experiment, inexperience, excess
6. pollute - populated, pollutant, depletion, protective
7. measure - metallurgy, absorption, measurement, damage
________ Grammar: Gerundial Constructions
IV. Join two sentences into one. Pay attention to the use of prepositions.
EXAMPLE: Nitrogen is used in metal industry. We know that.
We know of nitrogen being used in metal industry.
1. Silver and cooper are very good conductors of electricity. We are
aware of that.
2. Freon destructs the ozone layer. We are afraid of that.
3. Robots will replace men. The idea of that goes back to ancient
times.
4. Alice is making that hologram without any help. I was surprised at
that.
5. The students should study the properties of carbon. The professor
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insists on that.
6. Radioactive carbon should be used to date ancient things. The
scientists recommend that.
V. Rephrase the following questions and let your friend answer them.
Use the prepositions where necessary.
EXAMPLE: Do you mind if I use your computer?
- Do you mind my using your computer?
- No, I don't. You can use it whenever you want.
1. Would you mind if they create an intelligent robot?
2. Do you mind if I make a report on air pollution?
3. Do you insist that we should sign the Clean Air Act? (on)
4. Will they object if I use the laser without asking for their
permission? (to)
5. Do you believe that we will restore the ecological balance on the
planet? (in)
6. Are you sorry that you are late? (for)
VI. Open the brackets and use the gerund in the Active or Passive Voice.
1. Nobody is surprised at his (to receive) the Nobel prize for his
discoveries in optics.
2. We are interested in new technologies (to develop).
3. Environmentalists insist on our (to cut) releases of CO2 into the
atmosphere.
4. We hear of gases (to apply) to produce the flame temperature of
6,000 °F.
5. I object to acetylene (to mix) with air in the workshop.
6. We are against transport (to pollute) the atmosphere.
7. The inventor made a report on the laser (to use) in surgery.
VII. Restore the original sentences.
1. being cheap, the air, used, is, because of, in welding
2. steel, oxygen, being used, we know of, in making
3. has the merit of, the device, being reasonably up-to-date
4. does not mind, the student, being helped
5. our, objects to, the professor, carrying out the experiment
6. aircraft, is capable, lifting, helium, of
VIII. Correct mistakes in the following sentences.
1. Do you believe in life exist on other planets?
2. Would you mind my lating?
3. We insist their buying this robot.
4. He spoke about distant galaxies be observed through a telescope.
5. They are interested in materials producing without losses of energy.
6. If you do not observe the readings, you will result in the device
being break.
7. I don't mind be helped if you do not mind helping me.
IX. Translate the following sentences paying attention to different forms
of the gerund.
1. I require thermal power stations being closed because of their
damaging the environment.
2. We hear of biosilk having been invented.
3. Newspapers report of acid rains having destroyed life in several
Swiss lakes.
4. Global warming will cause polar ice melting.
5. It is difficult to imagine robots having explored ocean depths
autonomously.
6.I know of toxic gases having been used during the last experiment.
7. I am sure of having read this article earlier.
8. Safety rules insist on acetylene being stored in the liquid state
under pressure.
X. Translate the sentences into English using your active vocabulary.
1. Он не возражает против того, чтобы роботы выполняли эту
опасную работу.
2.Мы знали, что воздух используется в металлургии.
3.Крупные фирмы настаивают на том, чтобы роботы заменили
человека.
4.У студентов возникли трудности при определении свойств фреона.
5.Он отвечает за то, чтобы работа была закончена своевременно.
6.Вы можете рассчитывать на то, что он дает вам точную информацию.
7.Он жаловался на то, что я очень медленно работаю.
8.То, что он составил программу так быстро, было приятным
сюрпризом.
Reading and Speaking
I. Practice reading these words.
nitrogen ['naitrid33n] dioxide [dai'Dksaid]
ultraviolet ['Altra'vaislit] chlorine ['klo:ri:n]
II. Our manufacturing industry strongly depends on gases. Look through
the text and enumerate the industrial gases, mentioned there.
III. Read the text attentively for more information about industrial gases.
Industrial Gases
We know of many gases used in industry for making various products. They are called industrial gases. Some of them are man-made and some are found in their natural state. Let us consider the most important ones.
Colourless, odourless, tasteless, non-toxic, and non-flammable, nitrogen has many uses, including glass making, food conserving, preventing semiconductors from oxidation.
Oxygen is the second largest volume industrial gas used in producing steel, building bridges and making electric equipment.
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Being the most abundant element (98%) in the universe hydrogen has almost as many industrial uses as nitrogen and oxygen. It is needed in metal industry, in food industry for preparing margarine and in oil processing. Also, power stations depend on hydrogen cooling their high-speed turbine generators.
Can you imagine your life without eating ice-cream, spraying deodorants, drinking sodas, and fire fighting devices? All these things are possible due to carbon dioxide.
Some people believe that balloon flying is for children. Still, helium is a serious gas capable of rays detecting and aircraft lifting. It is also used in arc welding.
It is impossible to imagine present-day life without air con-ditioning, refrigerators, spraying aerosols, and packaging foam for the TV or VCR. However, freon, necessary for making these common things, is found depleting the ozone layer, which protects us from
the destructive solar ultraviolet radiation. That is why scientists all over the world insist on fluorocarbon refrigerants being banned.
Argon is a noble gas comprising 0.98% of the atmosphere and forming no-known chemical compounds. Colourless, odourless, tasteless and non-toxic, argon is mainly used in producing high-quality welding in stainless steel and aluminum industry-Chlorine gas is very toxic; nevertheless it protects us from falling ill by purifying drinking and swimming water. It also takes part in making many chemicals, including solvents, plastics, rubbers and pesticides.
Water-based paints and vinyl records are made with the help of acetylene, which has many other applications. Stored in a liquid state it is also used as a fuel producing a large amount of heat and the highest flame temperature (about 6,000F, or 3,300°C) of any known mixture of combustible gases. When burnt with the correct amount of air, acetylene gives a pure white light. For this reason it was once used for illuminating places where electric power was not available. The air itself is used as an industrial gas. It acts as a protective envelope for metals during the welding process because it does not react chemically with these metals or other elements.
IV. Try to complete the table without looking into the text. Compare your table with that of your partner.
| Gas | Properties | Application |
| ... | ... | ... |
V. Complete the sentences with suitable words from the box.
| rubbers | foam | acetylene toxic |
| helium | dioxide | man-made noble |
| non-flammable | air | oxygen odourless |
Gases used in industry for making all kinds of products are known as industrial gases. They can be classified as natural and.... The examples of natural gases are nitrogen,..., and hydrogen. The first largest industrial gas is nitrogen. It is colourless, tasteless,...,... and non-toxic. Breathing and combustion are impossible without oxygen. Hydrogen is the most abundant gas in the universe. Carbon... is used in producing lemonades and conserving food. Balloons are normally filled with..., The gases depleting the ozone layer are
known as fluorocarbons. They are necessary in air conditioning, refrigeration and making packaging.... Argon is a... gas applied in welding. Chemicals, such as solvents.... plastics, and pesticides are available due to chlorine, which is a very... gas. Water-based paints and vinyl records are made with the help of... that is also known for producing an extremely hot flame. Even the... is used as an industrial gas because it will not react chemically with any elements.
VI. Devise a questionnaire on the topic "Industrial Gases". See if your
friend can answer all the questions.
VII. What data does the text provide? Have you learnt any new things?
Do you think the use of fluorocarbons should be reduced? Is it possible
to reduce it?
Further Reading
I. Practise reading these words.
volcanoes [vDl'keinsuz] consequence ['konsrkwsns]
eutrophication ['jutrsfi'keijan] depletion [di'plkjan]
II. These words are taken from the text. Use the dictionary to find out
their meanings.
ash, n soil, n
stir, v vegetation, n
rot, v chlorofluorocarbons, n
blanket, v face, v
far-reaching, adj prospect, n
III. Discuss the following questions with your partner.
1. Why is air pollution considered a global problem today?
2. What are the consequences of air pollution?
3. Is it possible to minimize the bad consequences of air pollution?
If so, how?
4. Are all air pollutants man-made? Give examples.
5. Is there a problem of air pollution in your country?
IV. Gases are not only a component of the industrial process. They are
also its result. Unfortunately they often produce a damaging effect on the
environment. Read the text attentively to learn more about air pollution.
Air Pollution as the Major Problem of the Day
Since the 19th century we are getting increasingly worried about industry polluting breathing air in densely populated cities where the great majority of people live.
Not all air pollutants are man-made. For billions of years the air has been polluted by volcanoes throwing out tons of ash and smoke, dust stirred by the wind, gases given off by growing plants or by rotting animal and vegetable matter, salt particles from the oceans, etc. However, having discovered fire man added much to natural pollutants by burning fossil fuels. Sherlock Holmes for example, observed London "pea-soupers"1, blanketing the city for days. That's because Londoners used soft coal for heating their houses.
Let us review what we know about combustion. All fossil fuels naturally contain hydrogen, carbon and sulphur, present in plants and animals. Uniting with oxygen during combustion these gases result in forming water and releasing carbon monoxide, carbon dioxide and sulphur dioxide. Besides, oxides of nitrogen are produced in the air whenever there are high temperatures, be it2 a car spark or a lightning stroke. These natural processes have far-reaching consequences.
The oxides reacting with water in the air produce carbonic, nitric, nitrous, sulphurous and sulphuric acids. Acid rains have damaging effects on materials and the environment. An excess of nitrogen in the air, greater than the ecosystems are able to absorb results in destructing the biological balance of the soils and water (eutrophication). In the layers of the air close to the ground photochemical (photo-oxidizing) pollution causes the formation of 'bad ozone', called so because of its destructing effect on human health and vegetation. And vice versa, the 'good ozone' protecting us from solar ultraviolet (UV) radiation in the stratosphere is being depleted by NO (mainly from traffic) and by chlorofluorocarbons. The ozone layer depletion has damaging effects on human health and environment. The greenhouse effect consists in atmospheric gases (CO2,
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