Учебно-методическое пособие по чтению специальной литературы для студентов 1 курса физического факультета. Дроздова И.В - 24 стр.

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     D. deviate                               D. cause

     2. fraction, n.                          6. complexity, n.
     A. section                               A. symmetry
     B. attraction                            B. permittivity
     C. opposition                            C. difficulty
     D. small part, bit                       D. superiority

     3. crucial, adj.                         7. amplify, v.
     A. distinct                              A. multiply
     B. decisive                              B. increase
     C. thorough                              C. reduce
     D. faulty                                D. generate

     4. random, adj.                          8. temporary, adj.
     A. aimless                               A. speedy
     B. blurred                               B. slow
     C. accurate                              C. a short time only
     D. rapid                                 D. eternal


                                         Laser
The laser is a device that produces a beam of LIGHT that is both scientifically and
practically of great use because it is COHERENT LIGHT. The beam is produced by a
process known as stimulated emission, and the word “laser” is an acronym for the
phrase “light amplification by stimulated emission of radiation”.

1.       The meaning of “coherent” light is as follows: Light moves in the form of a
         wave, with crests and troughs. Like all other kinds of ELECTROMAGNETIC
         RADIATION, it can be characterized both by its frequency, or number of wave
         crests passing a given point per second, and by its wavelength, or distance
         between wave crests. (Beams of such radiation travel through a vacuum at the
         highest velocity anything can achieve). Different wavelengths of light are seen
         as different colours.

         Like radio waves, light can also carry information. The information is encoded
         in the beam as variations in the frequency or shape of the light wave. In fact,
         because light waves are of much higher frequencies than radio waves, they
         have a correspondingly higher information – carrying capacity.

         The smallest unit of light is the PHOTON, which may be thought of as a
         particle as well as wave. In beams of light from ordinary natural and artificial
         sources, these individual photon waves are not moving along together because
         they are not being emitted at precisely the same instant but instead in random
         short bursts. This is true even when the light is of a single frequency. Such