"The essence of science: ask an impertinent
and you are on the way to a pertinent answer"
- Imagine a sequence of particles undergoing identical Simple
Motion, such that each particle begins to move slightly after the one
it. The result is a traveling "Wave Motion". If all the
are connected, for example, in a string, the motion is described as a
continuous "Sine Wave".
- The Sine Wave is the simplest of all possible waves. A
wave is one in which the shape of the wave is repeated "periodically" -
regular fixed intervals.
- Five basic properties which describe periodic waves.
- Wavelength () -
Distance after which
begins to repeat (Units: metres).
- Frequency (f) - Number of waves passing a fixed
in one second (Units: Hertz).
- Wave period (T) - Time taken for one wave to pass
point (Units: seconds).
- Wave speed (v) - Distance travelled by the wave
per second (Units: m/s).
- Amplitude (A) - Maximum displacement of particle
comprise the wave from their equilibrium position (Units: metres).
- Frequency, wavelength and speed are related by,
- There are two basic types of traveling waves.
: Motion of the constituent particles is
right angles to the wave direction, e.g. waves on a string,
"stadium" wave, electromagnetic waves.
LONGITUDINAL : Motion of the constituent
particles is back
and forth in the direction of motion of the wave, e.g. sound waves, the
- Comparison of SHM and Waves
- The amplitude of the SHM of the particles which comprise a
is the same as the amplitude of the wave.
- The frequency of the SHM of the particles which comprise a
is the same as the frequency of the wave.
- Particles which comprise the wave typically do not move at the
of the wave, e.g. molecules of air do not move at the speed of
sound in air.
- Miscellaneous important facts :
- A wave "travels" from A to B. The particles that
wave do not move from A to B, they oscillate about their fixed
- A wave transmits energy from one point to another.
waves appear to be transverse - boats bob up and down
due to water
waves. However, a detailed study shows that the
of water actually perform a circular motion, which can be considered as
combination of transverse and longitudinal wave motion.
Fourier's theorem states that any periodic wave can be decomposed
into a sum of sine waves with differing frequencies and
amplitudes. This means that an
analysis of the properties of sine waves can be applied to any periodic
"In a packed
program tonight we will be talking to an out-of-work
contortionist who says he can no longer make ends meet."
Dr. C. L. Davis
University of Louisville