Contributed by:
Wave properties, Definitions, Types of waves, Damping, Wave Equations
2.
Wave Properties
• Waves are propagated by a vibrating
source
• Pulse – single disturbance created by a
single oscillation
• Periodic Wave – periodic disturbance
created by a continuously vibrating source
3.
Definition
• Mechanical Wave - transfer of energy
through a medium
• Waves can move over large distances, but
the particles of the medium only vibrate
about fixed positions
• Waves transport energy but not matter
• Mechanical waves must travel through a
medium
4.
Types of Waves
• Transverse – particles in medium vibrate
perpendicular to the direction of the wave
motion
crest
A
trough
6.
• Crest – max displacement
• Trough – minimum displacement
• λ – wavelength – distance between two
successive crests (or troughs)
• A – amplitude – maximum displacement
from the rest position
7.
Longitudinal Waves
• Particles vibrate parallel to the direction of
wave motion
9.
• Compression – wave particles are
compacted closely together
• Rarefaction – where particles are spread
out
• Wavelength – distance between two
corresponding in phase points
• Amplitude – maximum displacement from
rest
10.
Damping
• Initial amplitude of the wave depends on
the initial energy of the source
• Energy decreases over time, so the
amplitude does as well - damping
11.
Wave Equation
• The velocity of a wave is related to its
wavelength and frequency
• Velocity – speed the wave travels
• Frequency – number of cycles that pass a
given point per second (in Hertz)
- measured by crests per second
v = λf
12.
Example
• A wave has a wavelength of 5m and a
frequency of 3 Hz. What is its speed?
• A crest of a wave in a pool takes 2.5sec to
travel from one end to the other end (20m).
It is noticed that 10 crests pass by a mark
in 15 sec. What is the wavelength?
13.
• The frequency of a wave is determined by
the rate that the source produces them
• The velocity of a wave depends on the
properties of the medium
14.
Velocity of Transverse
• In transverse waves the velocity depends
on the tension (tightness) of the medium
and the mass/length of the medium
• Greater tension increase both v and f
v = √(Ft/(m/L))
15.
Example
• A wave of wavelength .30m is traveling
down a 300m long wire of mass 15kg. If
the wire is under a tension of 1000N, what
is the velocity and frequency of the wave?
16.
Longitudinal Velocity
• Velocity in longitudinal waves depends on
the elasticity(E) of the material and the
density(ρ) of the material
v = √(E/ ρ)
17.
Example
• You can hear a train approaching by
putting your ear to the track. How long
does it take for a sound wave to travel
1.0km down a steel track?
E = 2.0x1011 N/m2 and ρ = 7.8x103 kg/m3
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