Ответы 10: Module 10 - Ответы
Описание
module 10
LASER AND OPTICAL TECHNOLOGIES
1. Match the words (1-6) with their definitions (a-f). Use a dictionary if necessary.
1-f, 2-a, 3-b, 4-e, 5-d, 6-c
2. In groups answer the questions.
1-c, 2-a, 3- Light amplification by stimulated emission of radiation
Lab, uni –are examples of shortenings
Mr, don’t - are examples of contractions
3. Study the pictures below. Which of the following words and phrases refer to ordinary light (1) and which to laser light (2)?
1-its intensity decreases with distance, it is not strictly monochromatic as travels in the form of short pulses of small length, incoherent, travels in all directions, disorganised, less intense.
2-coherent, highly monochromatic, travels in one direction, highly intense; organized.
READING
Part 1
5. Find the words and word combinations in the text which have the following meanings.
§1
| §2
| §3
| §4, 5
|
1- remind 2-employ(ed) 3-remain 4-embody
| 5-amplification 6-emission 7-strengthen 8- (light) source. 9 - relatively (low intensity) 10-beam 11-spreading 12-decrease 13-in contrast 14- output
| 15- eventually 16- lay (laid) the foundation 17-award
| 18- due to 19-remarkable 20-turn out 21-record 22-vaporise 23- measure (distances) 24-accuracy 25-implement 26-prove crucial
|
7. Read the statements and decide which of them are true (T) and which are false (F) according to text 10A. Explain why.
1- F (not microwave but light); 2-F (1960); 3-F (Einstein proposed the theoretical possibility of the process that made laser possible); 4 - T; 5-F (lasers turned out to have myriads of uses in lots of different fields) 6-T; (the use of may expresses the possibility); 7-F (we are not talking about weapons but rather about laser-sighting devices); 8-T; 9-T (true according to the text, but some people might disagree); 10-T (according to the text)
READING
Part 2
11. Read the description of the diagram and match the words below with numbers 1-8 in the diagram.
1-the power source, 2-a tube of lightning, 3-atoms, 4-photons, 5-a ruby crystal, 6-a mirror, 7-a partial mirror, 8-a laser beam
12. You are going to read about how a laser beam is made. Before you read the text put these notes into the best order.
- escaping photons form a powerful laser beam (8)
- atoms absorb7 energy and give off a photon of light (3)
- the flashes inject8 energy into the crystal in the form of photons (2)
- partial mirror lets some photons escape (7)
- electric supply makes the tube flash on/off (1)
- new photon hits an excited atom which emits two photons instead of one (5)
- a mirror reflects photons along inside of crystal (6)
- new photons travel inside crystal at the speed of light (4)
14. Read the text in detail and choose the best option to complete the sentences according to the information from the text.
1-c, 2-c, 3-b, 4-b, 5-c, 6-a, 7-c, 8-b
READING
Part 3
16. Read the text and fill in the gaps with the words in boxes.
Part 1. Photonics
1- particles, 2-explore, 3-cure, 4-wavelengths, 5-suggested, 6-controversial, 7-confirmed, 8-entire, 9-visible and invisible, 10-cutting-edge,11- far-reaching
Part 2. How light really works
12- makes sense, 13- bouncing, 14-incoming, 15-excited, 16-photons, 17-solar panels, 18- reflecting, 19- absorbing, 20-cells, 21- photoelectric, 22-converted
18. Listening on the topic. Listen to a short lecture about lasers and decide which of the following points below the speaker talks about.
- Ø The unique characteristics of laser light.
- Ø How laser light is different from ordinary light
- Ø How lasers are used in the military.
- Ø How lasers are useful in eye surgery.
- Ø How laser was invented.
- Ø Different types of lasers.
- Ø The operation of a ruby laser.
- Ø How electronic transitions create stimulated emission.
- Ø How the light becomes intensified and narrowed in wavelength inside a laser cavity.
- Ø Innovations and improvements in laser technology.
https://www.youtube.com/watch?app=desktop&v=oUEbMjtWc-A
Tapescript + answers to questions in Ex. 19.
How a laser works
For years lasers have been a hallmark of science fiction, yet much of our technology today depends on them. Range finding devices, optical communications, and of course, bar code scanners. The unique characteristics of laser light make all these things possible.
However, its use by eye surgeons to reattach retina highlights them all. Injury can cause eye’s retina to peel away from the tissue supporting it. Without rapid treatment the entire retina can become detached causing blindness. Surgeons use green laser light of nearly a single wavelength because that colour passes through the eye’s lens and vitreous humor without being strongly absorbed and thus without causing damage. The laser beam then strikes the retina where the tissue strongly absorbs that light using high intensity light to weld the detached retina back into place. The beam’s narrowness allows the surgeon to affect only the area of retina that needs to be repaired, areas as small as thirty microns.
How a laser creates light with these three characteristics is a tour de force of engineering. Let me show you. Any glow-in-the-dark toy can illustrate basic principles of creating laser light. This glows because the zinc-copper based compound coating inside can absorb energy from a light source and then later radiate it as light. The light provides energy to electrons in the coating, promoting them to higher energy levels. Once the light is off, the electrons slowly lose their added energy and return to their lower energy ground states. The energy lost is given off as light. A closely related phenomenon lies at the heart of a laser.
Let me tell you about the engineering in the very first laser based on ruby. Here I have a tiny piece of ruby and some red coloured glass beads. When I shine the blue light on the glass beads nothing much happens. But shine it on the ruby and it glows red. Unlike the glow in the dark ball the light appears immediately. And when I shut off the blue light it disappears. In 1960 Ted Maiman demonstrated the first laser by taking a cylinder of ruby and surrounding it by a xenon arc flash lamp used in aerial photography. An intense burst of light from the lamp initiates lasing. To see how it works let’s look at what happens with weaker lamp. A flash would promote a few electrons from the ground state to an excited state. They would lose a bit of energy, fall to a lower energy state without emitting light and then drop from there to the ground state, giving off a burst of light. The light produced would be incoherent light, a spectrum of colours and intensities, just as my small laser made the ruby sphere glow.
Single wavelength
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