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1.1 Waves
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Motion of Waves
A boy is moving to and fro on a swing.
This type of motion is called an oscill
ation.
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Motion of Waves An oscillating or vibrating motion in which a
point or body moves back and forth along a lineabout a fixed central point produces waves.
Examples: Light waves are produced as a result of
vibrations of electrons in an atom.
Sound waves are produced by vibrating
mechanical bodies such as guitar strings or atuning fork.
Water waves are produced by a distur
banceon a still water surface.
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Motion of Waves Waves are carrier of energy .
They transfer energy from onelocation to another.
Waves transfer energy withouttransferring matter.
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Motion of Waves
The waves transfer energy from the stoneto the cork.
The cork does not moves outwards as the
wave passes because the water itself doesnot move outwards.
Conclusion: Energy is transferred from stone to the cork
which does not involved the transfer of wat
er.
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Transverse Waves
A transverse wave is one in which the
vibration of the medium is perpendi
cular to the direction of propagation of the wave.
Examples: water waves light waveselectromagnetic waves.
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Dierences
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Wave fronts
Water wave have crests and troughs.
A crest is the highest position of the wave. A trough is the lowest position of the wave.
"n waves lines #oining all the points ofthe same phase are called wave fronts.
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Wavelengths (λ)
The wavelength of a wave is the distance between two ad#acent points of the same
phase on a wave.
$" unit: m
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Amplitude (a)
The amplitude of a wave is its maximumdisplacement from its e%uilibrium position.
$" unit: m
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Period (T) !re"uenc# (f)
The period of a wave is the time takenfor an oscillation to complete one cycle.
$" unit: s The fre%uency of a wave is the number
of waves produced by a source in oneunit time.
$" unit: &' s()
T =1
f
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Wave $peed (v) The speed of a wave is the
measurement of how fast a crest ismoving from a fixed point.
$" unit: ms()
v = f
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Displacement%Time
&raph
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Displacement%Distance &raph
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'ample 1
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'ample
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"n an oscillating system such as the oscillationof a simple pendulum the oscillation does notcontinue with the same amplitude indefinitely
except when the system is oscillating in vacuum.
The amplitude of oscillation of the simplependulum will gradually decreases and
become 'ero when the oscillations stops. The decrease in the amplitude of an
oscillating system is called damping.
Damping
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Damping
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To enable an oscillating system to go oncontinuously an external force must be
applied to the system. The external force supplies energy to the
system. $uch a motion is called a forcedoscillation.
The fre%uency of a system which oscillatesfreely without the action of an external force iscalled the natural frequency .
Damping
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*esonance occurs when a system ismade to oscillate at a frequency
equivalent to its natural frequency by an external force.
The resonating system oscillates at its
maximum amplitude.
*esonance