CHAPTER 9 : WAVE MOTION
The transfer of energy in an elastic medium, without
the net transport of the medium, occurs through the propagation
of waves. The waves are formed due to the oscillation of the particles
in the medium which, in succession, transfer the energy from one
particle to another due to the elastic forces holding them together.
9.1 Transverse waves and Longitudinal waves
When the wave propagates along the transverse (perpendicular)
direction of the oscillation of the particles, then it is called
The diagrams represent schematically the formation
of a Transverse Wave. 0,1,2,3,4 particles of an elastic medium that
are equidistant from each other and capable of vibrating along the
vertical with the same amplitude (r), period (T). At t = 0, the
particle begins to vibrate, indicated by
. After T/4, 2T/4 , 3T/4, T the arrow shifts to 1st
to 2nd to 3rd to 4th particle,
due to the transfer of energy from one particle to another .
The characteristics of transverse waves are :-
Formation of troughs and crests.
Successive crests or troughs are separated
by constant distance
called wave length.
The wave progresses with velocity
where T is the period of wave in interval of time in which the
wave advances by
Frequency ( n) of waves is defined as number
of waves crossing any point in the medium per unit time i.e.
The dashed curves represent the position of the particles at different
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When the propagation of waves occurs along the
same direction as that of the oscillations of the particles, then
a longitudinal wave is formed. The diagrams above represent the
formation of longitudinal waves.
The characteristics of these waves are: -
Formation of compression and rarefaction .
The distance between successive compressions or rare factions
is called wave length l .
The wave propagates with velocity T
is period of wave.
Frequency of waves is n =
\ v = n l
9.1 Tranverse and Longitudinal
9.2 Equation of Linear, Progressive, Harmonic