Английский язык. Ч.3 (Units 9,10). Ильичева Н.А - 8 стр.

where the speed is greater, the ray bends away from the normal; this is shown in
Fig. 5b for a ray traveling from water to air. Refraction is responsible for a
number of com-mon optical illusions. For example, a pencil put in water appears
to be bent.




              Figure 5a.                                 Figure 5b.
(7;…)
   An interesting thing happens as the angle of incidence becomes larger. The
refracted ray is bent farther from the normal and at a particular critical angle Qc
the refracted ray is along the boundary of the two media. For angles greater
than Qc, the light is reflected and none is refracted. The phenomenon is called
total internal reflection (Fig. 6). Internal reflection enhances the brilliance of
cut diamonds. A diamond cut so that most of the light entering the diamond is
internally reflected. The light then emerges from only certain portions with a
brilliance far exceeding that of incoming light. This effect creates the diamond’s
sparkle.




                                    Figure 6.

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