Wave motion
(A) What is a wave?
Wave is a way of transferring energy by means of vibration. Waves transfer
energy without a transfer of matter.
(B) Transverse wave and longitudinal wave
Waves can be classified into transverse waves and longitudinal waves according
to the direction of vibration.
 A transverse wave is one in which the vibrations are at right angles to the direction
of travel of the wave. Examples: water waves, light.

A longitudinal wave is one in which the vibrations are along the direction of travel of
the wave. Example: sound.
(C) Terms for describing a wave

The amplitude A of a wave is the size of maximum disturbance measured from the

resting position.
The wavelength λ of a wave is the minimum distance in which a wave repeats

itself.
The frequency f of a wave is the number of complete waves produced in one second.
It is also the number of vibrations completed by a particle in the wave. It is measured
in hertz (Hz). The frequency of a wave is determined by the vibrating source.
Wave motion
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
The period T of a wave is the time taken for one wave to be produced. It is also the
time taken for a particle on the wave to make one complete vibration. T =

1
. The
T
period of a wave is determined by the vibrating source.
The wave speed v is the distance travelled by the wave in one second. It is
determined by the medium of the wave, except in the case of electromagnetic
waves in which the wave speed also depends slightly on frequency.
(D) Relationship between wave speed, frequency and wavelength
The relationship between wave speed v, frequency f and wavelengthλ is given by the
equation v = f λ.
(E)Vibrations in wave motion

Particles which are one wavelength apart vibrate in phase; particles which are
half a wavelength apart vibrate in antiphase. For example, in the following
transverse wave, particles a, i and g are vibrating in phase and a and e are
vibrating antiphase.

When a particle on a wave makes one complete vibration, the wave moves
forwards a distance equal to one wavelength.

A displacement-time graph shows the displacements of a particle on a graph at
different times. A displacement-distance graph shows the displacements of all the
particles on a wave at a certain time. (It should be noted that these two types of
graph are totally different.)
Wave motion
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