Lesson 2

Light Amplification by the Stimulated Emission of Radiation. Laser усиление света с помощью индуцированного излучения	coherent когерентный
monochromatic монохроматический (одноцветный)	to emit излучать
partially reflecting mirror частично отражающее зеркало	ruby laser рубиновый лазер
to coil обматывать, извиваться	intermittent прерывистый
to trigger вызывать, провоцировать, запускать	to excite возбуждать
to amplify усиливать	ruby laser лазер на рубиновом кристалле

7. Why do we call lasers the solution looking for a problem?

Reading and speaking activities Words and expressions from the text

		in (to do someone else’s job temporarily while they are not available to do it )
	stand
for (if a letter, an abbreviation, or a symbol stands for something, that is what it means or represents)

8. Fill in the gaps with the propositions.

1. The letters ERM stand ____ Exchange-Rate Mechanism.

2. Lorraine was ready to stand ___if Helen got sick.

9. Read the text. Be ready to describe the process of laser beam generation.

The acronym LASER stands for Light Amplification by the Stimulated Emission of Radiation. Laser light differs from ordinary light in three ways:

a) it is monochromatic, that is, it consists of a single wavelength (colour);

b) it is coherent (organised), that is, all the photons vibrate in phase with one another in space and time; and

c) it is highly directional(направленный), emitted as a relatively narrow beam in a specific direction(излучается в виде относительно узкого пучка в определенном направлении.).

The type of laser described in this lesson is the ruby laser, which uses a cylinder made of a ruby crystal. A fully reflecting mirror is placed on one end and a partially reflecting mirror on the other. A high-intensity light tube is coiled around the ruby cylinder to provide an intermittent (non-continuous) flash of white light that triggers the laser action. The flashes excite electrons in the atoms in the ruby to a higher energy level. Upon returning to their normal state, the electrons emit photons of ruby-red light. At first the photons are emitted in all directions. The mirrors reflect some of the photons up and down the cylinder. Photons from one atom stimulate emission of photons from other atoms and the light intensity is rapidly amplified. The mirrors reflect the photons back and forth inside the ruby crystal, continuing this process of stimulated emission and amplification. Finally, the photons leave the cylinder through the partial mirror. This is a beam of laser light.

10. Match the words and word combinations.

that is	быстро, стремительно
fully reflecting mirror	интенсивность
rapidly	световой колодец
intensity	направленный
differ from	вибрировать
light tube	полностью отражающее зеркало
vibrate [vaɪˈbreɪt]	вспышка
flash	отличаться от
directional	иначе говоря, другими словами

11. Fill in the gaps with the appropriate word.

(to) amplify amplified amplification

1. These stories only _amplified ________ her fears.

2. an ___amplified________ guitar

3. Would you care ________________ that remark?

4. …a number of such photons is proportional to coefficient of _____amplification

emit(ted) emission

1. He ___emits______ a low loan.

2. Pulsars ___emit________radiation.

3. Stimulate ____emission_____

intensity(intensified) intensify intensive

1. The cross-examination increased in __ intensity _________.

2. He was surprised by _____intensity__ of her emotions.

3. After six-months` __intensive__ training, she was ready to fly the aircraft.

4. Economic conditions _intensify__ the pressure on industry to raise prices.

partial partially part (noun, adverb)

1. The patient may only make a partial recovery.

2. He was only partially to blame for the accident.

3. What __part of America do you come from.

4. The medical exams are partially written, _________ practical.

Directional(напрвленный) direct(ed) direction

1. a directional antenna

2. His angry is mainly directed to his father.

3. Our efforts are primarily directed towards helping children who live in poverty

4. I`d give you a lift, but I`m going in the opposite direction.

reflect (ed) reflection

1. Anna stared at her reflection in the hall mirror.

2. The lake reflected the surrounding mountains.

3. Pale colours reflection light.

4. Your choice of clothes is reflect of your personality.

Coherent (связный) coherence

1. A common religion ensures the coherence of the tribe.

2. Finally! A textbook that provides a coherence approach to the subject.

3. My head hurt so much I couldn`t give a coherent answer.

12. Listen to part of a talk about lasers. Match the words in the box with the labels 1-8 in the diagram below.

ruby crystal atom light tube mirror power source photon laser beam partial [ˈpɑː.ʃᵊl] mirror

Script:

… and as Jenny said, my name is Lee. So, Jenny had been explaining what laser light is, and if there are no questions, we can now turn to the next section of the talk, in which I`m going to outline the basic components of a laser and at this point I`d like you to look at the diagram which is coming up on the screen now.

Right, basically you`re looking at a long red cylinder with a yellow zigzag tube coiled around it. Can you all see that?

Well, the red cylinder actually represents a ruby crystal, and the yellow zigzag represents a tube of light, rather like a fluorescent light tube. It coils around the ruby crystal and is of course connected to the power source shown in blue. When the laser is working, this light tube flashes intermittently, on and off like a series of camera flashes. Anyway, we`ll come to that later.

The grey disc to the left of the ruby crystal is a mirror and the one to the right of the crystal is a partial mirror, which means that it reflects part of the light, about 99% of it, in fact, but allows about 1% of the light to pass through it to the right. I think I`ve covered the main components. The large green circles inside the crystal represent atoms, and the small blue circles inside the crystal represent atoms, and the small blue circles represent photons, or particles of light. Finally, the large red arrow coming out of the right hand side of the machine is a laser beam.

OK, so before I hand over to Zak, are there any questions at this point? There will be a chance at the end of the complete talk to ask questions, so there`s no rush. Right, so now I`m going to hand over to Zak, who`s going to cover the next section of the talk, which…