Английский язык. Ч.3 (Tests 10,11,12). Ильичева Н.А - 9 стр.

itself. The new wavelet is the envelope of all the wavelets – that is, the tangent
to all of them.
   Huygen’s principle is particularly useful when waves impinge on an obstacle
and the wave fronts are partially interrupted. Huygen’s principle predicts that
waves bend in behind an obstacle. This is just what water waves do. The
bending of waves behind obstacles into the “shadow region” is known as
diffraction. Since diffraction occurs for waves, but not for particles, it can serve
as one means for distinguishing the nature of light.


                                Test 11 (Unit 10)


                          Special Theory of Relativity


A. Reading


   Read the text and choose from the list A–F the sentence which best fits each
gap in the text. There is one extra sentence which you do not need to use.


                       The Michelson-Morley Experiment
A. The Michelson-Morley Experiment was designed to measure the speed of the
   ether – the medium in which light was assumed to travel – with respect to the
   Earth.
B. The “null” result was one of the great puzzles of physics at the end of the
   nineteenth century.
C. It is assumed that the “ether wind” is moving with speed v to the right.
   Alternatively, the Earth is assumed to move to the left with respect to the
   ether at speed v.
D. The medium for light waves could not be air, since light travels from the Sun
   to the Earth through nearly empty space.
                                         9