WAVES - SDA
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A wave is a result of disturbances that are repeated regularly and passed on from one particle to
another or one section to another in the medium.
A medium is a region through which waves travel.
When a wave travels through the medium, particles or sections in the medium do not travel with the
wave but only undergo vibrations or variations about their mean or rest positions.
TYPES OF WAVES:
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Longitudinal
Transverse
Longitudinal waves:
A longitudinal wave is that where particle vibration in the medium is in line with the wave direction.
Illustration:
particle vibration
wave direction
A longitudinal wave consists of compressions and rarefactions.
A compression is a region in the medium where the particles are closer to one another, while a rarefaction is
that where the particles are far apart.
Illustration
C - compression
R – rare-faction
λ - wavelength
An example of the longitudinal wave is the sound wave.
Transverse waves:
A transverse wave is that where particle vibrations in the medium are perpendicular to the wave direction.
Illustration:
particle vibration
wave direction
A transverse wave consists of a series of crests and troughs.
crest
Illustration:
trough
Examples of transverse waves are; water waves, electromagnetic waves such as light, radio waves, ultraviolet
etc.
Terms used to describe waves:
Illustration:
P
Q
λ
displacement
a
O
B
A
distance
λ = PQ = OA =AB
Wavelength (λ):
Wavelength is the distance travelled by a complete wave. (Or, is the distance between two successive and
corresponding positions in the wave. Or, Is the distance between two successive crests or troughs. Or Is the
distance between two successive compressions or rarefactions)
Amplitude (a):
Is the maximum displacement of the particle in the medium about its rest position.
Frequency (f):
Is the number of waves per unit time (in one second).
The S.I. unit of frequency is the hertz (Hz)
Period (T):
Is the time taken to complete one wave.
Note:
Period =
1
frequency
OR
T= 1
f
Frequency =
Velocity or speed of the wave (v):
Is the distance travelled by the waves per unit time.
Relationship between velocity, frequency and wavelength:
Velocity = frequency x wavelength
(v = f λ)
Wavefront:
Is a line joining corresponding parts of the wave that are in step or in phase.
1
period
f = 1
T