The following graphs represent continuous waves (as opposed to
the single pulses shown here). 

These graphs have the same shape as graphs
of sine of angle against angle. 

For this reason the waves they describe are often called
sine waves (or sinusoidal waves, if you want to sound more
intelligent). 

This is the type of wave which results when the disturbance of
the medium is produced by a body oscillating with simple
harmonic motion, s.h.m. 



Graph of Displacement of the Medium against Distance
along a Typical Wave 







The maximum displacement of the medium from the equilibrium
position, r, is called the amplitude of the wave. 



λ is
the wavelength. 

This is the distance moved by the disturbance during one time period
(see below). 



For a transverse sine wave, this graph can be considered to be a
picture of the wave at a given instant in time. 

However, it should be remembered that the graph could also
represent a longitudinal wave. 



Graph of Displacement of a Particular Point in
the Medium against Time for a Typical Wave 







T, is the time for one "cycle" of the wave. 

This is called the time period. 



The frequency, f, of the wave is the number of cycles per
second. 

This is determined solely by the source of the waves
(the frequency of a wave is equal to the frequency of the
source). 

As with any cyclical phenomenon, the relation between frequency
and time period is 





Relation between f,
λ and
Velocity of Propagation, v 

As stated above, λ is the distance
moved by the disturbance during one time period. 



From the definition of velocity we have 



where s is distance moved and t time taken. 

So, in the particular case of a disturbance forming a wave we can
write this as 



therefore 



This relation shows us that, for a given velocity, the wavelength is
inversely proportional to the frequency. 

In other words, as frequency increases wavelength decreases. 
