class 39 stationary standing waves · 2018. 9. 1. · class 39 stationary standing waves author:...
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PHYSICS Waves Mr R Gopie
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STATIONARY STANDING WAVES
A stationary wave is produced by the superposition of a coherent progressive waves which
are travelling in opposite directions-‐ for instance, such a stationary wave is produced when a
progressive wave train is reflected normally (i.e. back along itself) by a suitable reflecting boundary
or surface.
Along a progressive (or travelling) wave, neighbour oscillations involved in the propagation
of the wave have the same amplitude (if there is no significant energy loss as the wave travels
along). However, neighbouring oscillations are out of phase with each other. Also, there is a net
energy transfer of energy in the direction of propagation of the wave.
Along a stationary (or standing) wave:
a) Neighbouring locations have different amplitudes of oscillation. In fact, there are locations
where the displacement is permanently zero (i.e. there are no oscillations at these
locations) -‐ such locations are called nodes. There are also locations (half-‐way between
adjacent nodes) where the amplitude of oscillation is a maximum – such locations are called
antinodes. The distance between adjacent nodes, or adjacent antinodes, represents half of a
wavelength (i.e. λ/2).
b) For all locations between adjacent nodes the oscillations are all in phase with one another.
c) There is no net transfer of energy along the wave (since the energy cannot get pass the
nodes.
Stationary waves can be produced with transverse waves (such as those along stretched, vibrating
strings and all e.m. waves such as visible light and microwaves), and also with longitudinal waves
(such as sound waves, as produced in pipes or tubes, for instance)
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Consider how the waveform of a stationary wave changes with time
Diag. 17
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TUTORIAL
June 1997 paper 2 #3
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June 1999 paper 2 #3
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January 1999 paper 2 #3
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June 1992 paper 2 #5
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June 2006 paper 2 #3
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June 2000 paper 2 #2
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