Language activity

Exercise 1. Summarize your knowledge of the functions of the verb “to be”. Translate the following.

1. The microscope has been improved and refined continuously throughout its history, that is practically since the 17^th century.

2. The main characteristics to be refined have always been the resolution and the elimination of aberrations.

3. The projection lens is to be especially corrected for curvature of field and distortion.

4. The purpose of the condenser is to concentrate the light coming from the mirror to a point approximately 1.25mm above the surface of its top lens.

5. The magnifying power of microscopes is being increased from year to year.

Exercise 2. State different meanings of “that (those)”.

1. тот, этот

2. что

3. который

4. заменитель существительного (that of)

5. то есть [that is = i.e. (id est - лат.)]

6. именно, только лишь (it is …that – усилительный оборот)

7. то, что

1. It is also worth pointing out that ruby lasers were extensively used in the past for military rangefinders.

2. Gas lasers are usually excited by electrical means, i.e., pumping is achieved by passing a sufficiently large current through the gas.

3. One of the most characteristic features of the He-Ne laser is that the output power does not increase monotonically with discharged current but reaches a maximum and thereafter decreases.

4. Since these pure rotational lasers are relatively less important than the other categories, we shall not discuss them further in the sections that follow.

5. That metals are good conductors of electricity is known to everybody.

6. It was the nature of p-n junction that happened to be one of the most difficult things for scientists.

7. At that time the engineers were testing a new semiconductor for the application in industry.

8. Semiconductor is a material having an electrical conductivity intermediate between that of metals and insulators.

9. Output energy and peak power in Q-switched operation are comparable to those obtainable with a Nd:YAG rod of comparable dimensions.

10. This was the laser scheme that was proposed in the original paper of Schawlow and Townes.

Exercise 3. Summarize your knowledge of Present Simple or Present Continuous. Put the verbs in brackets into the correct tense.

1. A lens (to be) a piece of glass, plastic or other transparent material curved on one or both sides.

2. Lenses (to refract) the light rays from an object forming an image.

3. I (to use, never) my mobile phone if I (to drive).

4. The walls of the house (to absorb) heat day after day.

5. The news bulletin (to begin) at 6 p.m.

6. In spring the days (to grow) longer and the nights (to become) warmer.

7. Jack often (to go) to the theatre. On Saturday he (to go) to see a new play.

8. Electromagnetic waves (to travel) in all directions through the Universe.

9. Some people still think the sun (to go) round the earth.