Unit 8. Electromagnetic Spectrum. Active vocabulary
1. Electric arc [ɪˌlektrɪk'ɑːk] електрична дуга, дуговий
розряд
2. Electromagnetic radiation електромагнітне
[ɪˌlektrə(u)mæg'netɪkˌreɪdɪ'eɪʃ(ə)n] випромінювання
3. Electromagnetic spectrum спектр електромагнітних
[ɪˌlektrə(u)mæg'netɪk'spektrəm] хвиль
4. Electromagnetic wave електромагнітна хвиля
[ɪˌlektrə(u)mæg'netɪk'weɪv]
5. (To) emit [ɪ'mɪt] випромінювати
6. Gamma rays ['gæməreɪz] гамма-проміння
7. Infrared [ˌɪnfrə'red] інфрачервоний, інфрачервоне випромінювання
8. Microwave ['maɪkrəweɪv] мікрохвильовий, мікрохвиля
9. Radio wave ['reɪdɪəuweɪv] радіохвиля
10. Ultraviolet [ˌʌltrə'vaɪələt] ультрафіолет(овий), УФ-випромінювання
11. Visible light ['vɪzəb(ə)l'laɪt] видиме світло, хвилі видимої частини спектру
12. Wavelength ['weɪvleŋθ] довжина хвилі
13. X-radiation ['eksˌreɪdɪ'eɪʃən] рентгенівське випромінювання
14. X-ray ['eksreɪ] рентгенівський промінь
Pre-reading task
Exercise 102. In pairs, answer the following questions.
1. What waves of the electromagnetic spectrum do you know?
2. Give several examples of electromagnetic waves that are encountered in everyday life.
Exercise 103. Read, translate the text and answer the questions below it.
Electromagnetic waves
Light is energy that is emitted by accelerating charges – often electrons in atoms. This energy travels in a wave that is partly electric and partly magnetic. Such a wave is an electromagnetic wave. So, an electromagnetic wave is composed of oscillating electric and magnetic fields that regenerate each other. Electromagnetic waves move outward from a vibrating charge. No medium is required. At any point of wave, the electric field is perpendicular to the magnetic field, and both are perpendicular to the direction of motion of the wave. Electromagnetic waves move at the speed of light – no matter what the frequency or wavelength or intensity of the radiation.
The electromagnetic spectrum is a continuous range of waves extending from radio waves to gamma rays (Fig. 11). The electromagnetic spectrum consists of radio waves, microwaves, infrared, visible light, ultraviolet rays, X-rays and gamma rays.
Radio waves have wavelengths that are comparable to the size of a radio antenna, i.e. meters to tens of meters. Radio waves are produced by changing currents in a conductor. They can be used in media and communication.
Microwaves were named so because they have much shorter wavelengths than radio waves. When food heats unevenly in a microwave oven, the small distances between neighboring hot and cold spots is half of one wavelength of the standing wave the oven creates. Microwaves are produced by changing currents in a conductor and can be used in microwave cooking and communication devices (mobile phones, etc).
Infrared (IR) light is electromagnetic radiation with a wavelength longer than that of visible light. This wavelength corresponds to a frequency range of approximately 1 to 400 THz, and includes most of the thermal radiation emitted by objects near room temperature. Microscopically, IR light is typically emitted or absorbed by molecules when they change their rotational-vibrational movements. Infrared light is used in industrial, scientific, and medical applications. Night-vision devices using infrared illumination allow people or animals to be observed without the observer being detected. In astronomy, imaging at infrared wavelengths allows observation of objects obscured by interstellar dust. Infrared imaging cameras are used to detect heat loss in insulated systems, observe changing blood flow in the skin, and overheating of electrical apparatus.
The visible spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light or simply light. A typical human eye will respond to wavelengths from about 390 to 750 nm (frequency – 400–790 THz). A light-adapted eye generally has its maximum sensitivity at around 555 nm (540 THz), in the green region of the optical spectrum. The spectrum does not, however, contain all the colors that the human eyes and brain can distinguish. Unsaturated colors such as pink, or purple variations such as magenta, are absent, for example, because they can be made only by a mix of multiple wavelengths.Visible light is emitted by the Sun. Intense light can damage your sight.
Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm. It is named because the spectrum consists of electromagnetic waves with frequencies higher than those that a human identifies as the colour violet. These frequences are invisible to a human, but visible to a number of insects. UV light is found in sunlight and is emitted by electric arcs and specialized lights such as black lights. It can cause chemical reactions, and causes many substances to glow or fluoresce. Although ultraviolet radiation is invisible to the human eye, most people are aware of the effects of UV through sunburn, and in tanning beds. Ultraviolet is also responsible for the formation of vitamin D in all organisms. The UV spectrum thus has many effects, both beneficial and damaging, to human health.
X-radiation (composed of X-rays) is a form of electromagnetic radiation. X-rays have a wavelength of 10 to 0.01 nanometers, frequencies from 30 petahertz to 30 exahertz. They are shorter in wavelength than UV rays and longer than gamma rays. X-rays are emitted by electrons outside the nucleus. X-rays can penetrate into solid objects, and their largest use is to take images of the inside of objects in diagnostic radiography and crystallography. X-rays have a wide variety of medical uses such as: in medical imaging (e.g. CN scans – computed tomography), for diagnostic purposes (X-rays are especially useful in the detection of pathology of the skeletal system). They are also used in airport security baggage scanners. X-rays are hazardous because they cause damage at a cellular level; and thus they can cause cancer by damaging cells.
Gamma rays or gamma radiation is electromagnetic radiation of high frequency (very short wavelength). They are produced by sub-atomic particle interactions such as radioactive decay, fusion, fission etc. Gamma rays have frequencies 1020 Hz, and therefore have energies above 100 keV and wavelength less than 10 picometers, often smaller than an atom. Gamma-rays have a wide variety of medical uses such as: in CT scans and radiation therapy, gamma rays are used to treat some types of cancer killing cancerous cells (so called gamma-knife surgery) and for diagnostic purposes in nuclear medicine. Gamma ray can be also used for measuring the thickness of materials. However, gammar rays are hazardous because they cause damage at a cellular level, and they can cause cancer by damaging cells (from ‘Conceptual Physics’).
1. What is an electromagnetic wave?
2. How is an electromagnetic wave created?
3. How fast does an electromagnetic wave move?
4. Name all the parts of the spectrum (from longest to shortest wavelength).
5. What waves are dangerous?
6. Circle the letter beside each statement that correctly describes electromagnetic waves.
a) No medium is required to produce the waves.
b) The electric field is parallel to the magnetic field in the waves.
c) The waves move outward in all directions from the vibrating charge the created them.
d) Both electric and magnetic fields are perpendicular to the direction of motion of the wave.
Exercise 104. Circle the correct answer.
1. Which of the following is correct in order of lowest to highest frequency?
a) X-rays, visible Light, microwave
b) Ultraviolet, visible Light, gamma rays
c) Microwave, visible Light, gamma rays
2. This type of emission maps the dust between stars.
a) Infrared c) X-rays
b) Ultraviolet d) Gamma-rays
3. Gas in space emits radio waves.
a) True b) False c) We don't know
4.This type of emission can come from radioactive materials.
a) Radio b) X-rays c) Gamma-rays
5. It’s possible to produce electromagnetic waves by shaking a charged rod back and forth in empty space.
a) True b) False
Exercise 105. Fill in the table “Electromagnetic Waves”.
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Produc-tion |
Uses |
Hazards |
Wave-length (m) |
Frequ-ency (Hz) |
Gamma rays |
Emitted during radioac-tive decay |
Measuring the thickness of materials, medical uses |
Causes cancer by damaging cells |
× |
×10 |
X-rays |
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Ultra-violet |
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Visible light |
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Infra red |
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Micro-waves |
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Radio-waves |
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Exercise 106. Match the items on the right to the items on the left to assemble the waves in the correct order.
1. Radio waves a) the highest frequency waves in the EM spectrum
2. Microwaves b) these waves are used to inspect luggage in airport security
3. Gamma rays c) these waves make your gin & tonic glow.
4. Infra red d) emitted by the laser in CD & DVD drives
5. Light e) the waves used for TV remote controls
6. Ultra violet f) used for mobile phones and radar
7. X-rays g) these waves have the longest wavelength in the EM spectrum
Exercise 107. Find the term in the puzzle that fits each clue given below. Then write the term on the line next to the clue.
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7. Distance between adjacent peaks in a series of periodic waves.
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Grammar. Infinitive and Gerund.
Exercise 107. Check your knowledge of infinitive and gerung doing the quiz below. Circle the correct answer.
‘Gerund or Infinitive’ Quiz
1. I’m worried … a job interview.
a) with having b) about having c) to have
2. … the game surprised us.
a) winning b) we won c) to win d) we win
3. Who is responsible … dinner in your house?
a) to cook b) for cooking c) that they cook d) of cooking
4. I’m sure … here will please them.
a) you being b) you are c) you to be d) your being
5. What do you think … a taxi to the airport?
a) to take b) your taking c) about taking d) taking
6. I’m tired … on this research paper.
a) for work b) to work c) of working d) about working
7. Was the teacher’s … clear?
a) explaining b) explained c) explain d) explanation
8. We insisted … at the meeting.
a) to be heard b) on being heard c) to hear d) on hearing
9. Please ask them … in the classroom.
a) don’t smoke b) not to smoke c) not smoking d) don’t to smoke
10. I was lucky … such a good grade.
a) of getting b) to get c) to getting d) get
11. I remember … the Queen in London. a) meet b) to meet c) meeting d) to meeting
12. Did you remember … the letter? a) post b) to post c) posting d) to posting 13. I'm not used … up this early. a) get b) to get c) getting d) to getting
14. I used … to the cinema a lot. a) go b) to go c) going d) to going 15. I regret … Mary about the wedding. a) tell b) to tell c) telling d) to telling 16. Mrs Jones, I regret … you that your credit limit has been exceeded. a) inform b) to inform c) informing d) to informing 17. Stop … this terrible noise at once! a) make b) to make c) making d) to making 18. I wanted to stop … some presents, but we didn't have enough time. a) buy b) to buy c) buying d) to buying
19. Look, it's starting … . a) rain b) to rain c) raining d) to raining 20. I started … English when I was four. a) learn b) to learn c) learning d) to learning
21. I am interested … your class.
a) to take b) to taking c) in taking d) in took
22. They enjoy … movies.
a) watching b) watch c) to watch d) to watching
23. We look forward … the Olympics.
a) at watching b) to watching c) to watch d) watching
24. I am bad … .
a) on ice skating b) at ice skating c) at ice skate d) with ice skating
25. I can't imagine … out of an airplane.
a) jumping b) at jumping c) to jump d) jump
26. The boss would like … more.
a) us to work b) we working c) us work d) him working
27. They allowed … home early
a) him to go b) he to go c) him going d) we to go
28. We invited … with us.
a) him come b) them coming c) she to come d) them to come
29. The neighbors are fed up … his house.
a) with him not clean c) with him not cleaning
b) to him not cleaning d) at him not to clean
30. The mother won't tolerate … up late.
a) Sara to stay b) she staying c) Sara staying d) her to staying
31. I persuaded … the team.
a) him to join b) his to joining c) he to join d) him to joining
32. She is nervous … alone.
a) about we travelling c) about us travelling
b) with us travel d) at us to travel
33. She refuses … to her mother
a) listen b) to listening c) to listen d) listening
34. We agreed … together.
a) working b) to work c) worked d) to working
35. I need … .
a) studying b) to study c) in study d) to studying
36. They postponed … the game because of rain.
a) playing b) to playing c) at play d) at playing
37. They want … good grades.
a) getting b) to get c) to getting d) get
38. Michael Jordan is good … basketball.
a) playing b) at playing c) with playing d) in paly
39. I regret not … my parents. a) hug b) with hugging c) to hug d) hugging
40. The criminal admits … the money.
a) on taking b) take c) to take d) taking
41. Many drivers avoid … in traffic.
a) driving b) to drive c) to driving d) drive
42. The gambler was angry … his money.
a) with lose b) to losing c) to lose d) at losing
43. Good teachers always offer … their students.
a) help b) to help c) helping d) to helping
44. I would like … a movie.
a) to see b) seeing c) to seeing d) see
45. The president wishes … violence.
a) to ending b) on ending c) ending d) to end
Writing
Exercise 108. Translate the following sentences into Ukrainian using active vocabulary.
1. Джерело електромагнітних хвиль – це заряджені частинки, які прискорено рухаються. 2. Об’єднавши всі електромагнітні хвилі, ми отримаємо cпектр електромагнітних випромінювань. 3. Спектр електромагнітних хвиль – це безперервна послідовність частот і довжин хвиль електромагнітних випромінювань. 4. Інфрачервоне випромінювання на шкалі електромагнітних випромінювань займає місце між радіохвилями та видимим світлом. 5. Усі нагріті тіла випромінюють інфрачервоні промені. 6. Джерелами цих променів є сонце, лампи розжарювання, електрична дуга, тощо. 7. Речовини, прозорі для видимого світла (наприклад, вода) непрозорі для інфрачервоного, і навпаки, непрозорі тіла для видимого світла (наприклад, чорний папір) стають прозорими для інфрачервоного.
8. Ультрафіолетове випромінювання – невидиме для ока випромінювання, яке отримують за допомогою тліючого розряду. 9. Довжина хвиль для ультрафіолетового випромінювання менша, ніж для видимого світла. 10 Джерелом цього випромінювання також є сонце, зорі, високотемпературна плазма. 11. Рентгенівські хвилі – електромагнітні хвилі, коротші за ультрафіолетові. 12. Рентгенівські промені здатні проходити через матеріали, непрозорі для світла. 13. Найкоротшими на шкалі електромагнітного випромінювання є гамма-промені. 14. За своїми властивостями гамма-промені дуже схожі на рентгенівські, але їх проникаюча дія набагато більша, ніж у рентгенівських променів.
Speaking
Exercise 109 . Role-play ‘Conference’.
Home task: Prepare a report on topic ‘Electricity and Magnetism’. Write out the main terms and prepare 5 questions for your groupmates based on your report.
Class work: Listen to the presentations of other students. Make notes while you are listening and ask questions. Choose the best presentation and the best presenter.