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Tuesday, 03 June 2008 00:00 |
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Applet shows two waves
travelling to the right. Imagine they are travelling along
the same line, but they are shown to be travelling along
parallel paths as a matter of convenience. When the two waves
are received by a particle, the resultant vibration the
particle would execute is shown in yellow. You can change the
frequency difference beween the waves and the phase
difference. Observe the motion of the white dots. It is the
particular particle you could focus on. Except in case when
the frequency difference is zero, you would see the phase
differnece between the oscillations varying with time. Since
the resultant amplitude depends on the phase difference
between the two oscillations you see maximum amplitude when
they are in phase and minimum when they are out of phase.
They keep getting in and out of phase resulting in maxima's
and minimas at different times at the same place. We call
this interference in time. The number of times the particle
gets in and out of phase would depend on the frequency
difference between the waves. If you increase the frequency
difference, you would see larger number of maximas and
minimas.
Do also observe the case of
zero frequency difference. You would see that the waves have
the same phase difference at all times giving rise to
resultant oscillations of constant amplitude- either zero or
twice the amplitude of one of the waves depending on whether
phase difference is PI or zero .
Surendranath Reddy. B.
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