An Introduction to
Waves
3U Physics
What is a wave?
A wave is a disturbance which carries energy from
one location to another.
What is a wave?
A wave is a disturbance which carries energy from
one location to another.
The material the disturbance travels through is the
?
The movement of the disturbance is referred to as
?
What is a wave?
A wave is a disturbance which carries energy from
one location to another.
The material the disturbance travels through is the
medium.
The movement of the disturbance is referred to as
?
What is a wave?
A wave is a disturbance which carries energy from
one location to another.
The material the disturbance travels through is the
medium.
The movement of the disturbance is referred to as
propagation.
2 Types of Waves
A longitudinal wave is a wave in which the particles of
the medium move in a direction parallel to the
direction of propagation.
2 Types of Waves
A longitudinal wave is a wave in which the particles of
the medium move in a direction parallel to the
direction of propagation.
2 Types of Waves
A longitudinal wave is also called a pressure wave
or a sound wave.
2 Types of Waves
A longitudinal wave is also called a pressure wave
or a sound wave.
The regions of increased pressure/density are
called ?.
The regions of decreased pressure/density are
called ?.
2 Types of Waves
A longitudinal wave is also called a pressure wave
or a sound wave.
The regions of increased pressure/density are
called compressions.
The regions of decreased pressure/density are
called ?.
2 Types of Waves
A longitudinal wave is also called a pressure wave
or a sound wave.
The regions of increased pressure/density are
called compressions.
The regions of decreased pressure/density are
called rarefactions.
2 Types of Waves
A transverse wave is a wave in which the particles of
the medium move in a direction perpendicular to the
direction of propagation.
Although sound waves are not transverse waves, we
often represent them as transverse waves because
transverse waves are easier to draw.
2 Types of Waves
The vertical axis represents not displacement but
pressure.
Snapshot of a Transverse Wave
The dashed line represents the equilibrium position of
the particles.
Snapshot of a Transverse Wave
The positions of maximum displacement are referred to as
crests (positive displacement) and troughs (negative).
The maximum displacement is the amplitude.
Snapshot of a Transverse Wave
The positions of maximum displacement are referred to as
crests (positive displacement) and troughs (negative).
The maximum displacement is the amplitude.
Amplitude = Energy
Snapshot of a Transverse Wave
The distance between one crest and the next crest (or
one trough and the next trough) is the
Snapshot of a Transverse Wave
The distance between one crest and the next crest (or
one trough and the next trough) is the wavelength,
represented by
Snapshot of a Transverse Wave
The distance between one crest and the next crest (or
one trough and the next trough) is the wavelength,
represented by l.
Snapshot of a Transverse Wave
The time it takes one complete wavelength to pass a
single point is the
Snapshot of a Transverse Wave
The time it takes one complete wavelength to pass a
single point is the period, represented by
Snapshot of a Transverse Wave
The time it takes one complete wavelength to pass a
single point is the period, represented by T.
Snapshot of a Transverse Wave
The time it takes one complete wavelength to pass a
single point is the period, represented by T.
t
T
# of cycles
Snapshot of a Transverse Wave
The number of complete wavelengths that pass a single
point in one second is the frequency, represented by f.
1
1
f  or T 
T
f
Frequency
Frequency is measured in units of 1/s or s-1
or Hertz (Hz).
“I do not think that the wireless waves I have discovered will
have any practical application.”
Wave Speed
The speed of a wave is therefore:
d
v
t
Wave Speed
The speed of a wave is therefore:
d l
v

t T
Wave Speed
The speed of a wave is therefore:
d l
v
  lf
t T
Wave Speed
The speed of a wave is therefore:
d l
v
  lf
t T
The speed of a sound wave in air at room temperature
(20oC) is 344 m/s.
Sound Wave Example
Calculate the wavelength of the sound wave
produced by a 125 Hz tuning fork in air at 20oC.
Sound Wave Example
Calculate the wavelength of the sound wave
produced by a 125 Hz tuning fork in air at 20oC.
v  344 ms
f  125 Hz
l ?
Sound Wave Example
Calculate the wavelength of the sound wave
produced by a 125 Hz tuning fork in air at 20oC.
v  344 ms
f  125 Hz
l ?
v
v  lf  l 
f
344 ms
l
 2.75 m
125 Hz
More Practice
Inquiry Activity: Slinky Waves
Homework: An Introduction to Waves