Английский язык. Ч.3 (Tests 10,11,12). Ильичева Н.А - 4 стр.

   Diamonds achieve their brilliance from a combination of dispersion and total
internal reflection (5;…). Incident light therefore strikes many of the internal
surfaces before it strikes one at less than 25° and emerges. After many such
reflections, the light has traveled far enough that the colours have become
sufficiently separated to be seen individually and brilliantly by the eye after
leaving the crystal.


A. This spreading of white light into the full spectrum is called dispersion.
B. You can see rainbows when you look at falling water droplets with the Sun at
   your back.
C. White light passes through a slit and an interference pattern is observed on a
   screen.
D. The colour of the light is related to the wavelength or frequency of the light.
E. Because diamonds have a very high index of refraction of about 2,3, the
   critical angle for total internal reflection is only 25°.
F. Although human eyes are not sensitive to UV or IR, some types of
   photographic film do respond to them.


B. Choose the correct item to fill in the gaps
1. When a crest of one wave arrives at the same time as a crest of another wave,
  the amplitudes of two waves add to form a larger amplitude. This is …
   interference (positive, productive, constructive).
2. When light strikes a transparent medium, some light is reflected and some is
  ... (transported, transmitted, carried through).
3. For angles greater than Qc, the light is reflected and none is refracted. This
   phenomenon is called … internal reflection (absolute, complete, total).
4. When light passes from air into a … medium as glass, the rays are refracted
  or “bent” toward the normal (more condensed, denser, more compressed).


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