Foundations of Physics
Mechanical Wave Notes
Types of Waves
Mechanical Waves – Wave that requires the a medium to
transfer energy from one location to another.
• Medium is the term used to describe the material or
substance the wave moves through.
• As the wave moves through the medium, its particles will
oscillate back and forth, but do not actually move with
the wave.
• Mechanical Waves can be categorized based on how
the medium oscillates as the wave passes through it.
Types of Waves
• Transverse Waves – Are mechanical waves in which the
direction the wave travels is perpendicular to direction the
medium oscillates.
Wave travels
Crest
Medium
oscillates
Trough
• Examples of transverse waves include secondary (s) seismic
waves (produced during earth quakes), vibrating strings of a
musical instrument, and stadium waves.
Types of Waves
• Longitudinal (Or Compression) Waves – Are
mechanical waves in which the direction the wave
travels is parallel to the direction the medium oscillates.
Wave travels
Medium
oscillates
Compression
Rarefaction
• Examples of longitudinal / compression waves include
sound, and primary (p) seismic waves (produced during
earthquakes).
Types of Waves
• Surface waves are similar to transvers waves except
the medium moves is small circles instead of just back
and forth.
• Surface waves most often occur at the surface of large
bodies of water like lakes and oceans.
• Electromagnetic Waves are also similar to transverse
waves made up of oscillating electric and magnetic fields
which are perpendicular to each other.
• EM waves are not mechanical waves.
Wave Characteristics
Frequency - The number of waves that pass a point in a
certain amount of time.
• Measured in Hertz (Hz)
• 1 wave per second = 1 Hz
Period - The time it takes for one wave to pass a point is
called the Period.
• Period can be measured in any unit of time
If the period of the wave is measured in seconds, then the
frequency of the wave is equal to the reciprocal of the period.
Frequency
1

1
Period
Wave Characteristics
Wavelength - The length of one wave oscillation.
• Measured from one point on a wave to the exact same
point on the next wave.
• Measured in meters (cm, mm, nm).
Wavelength and frequency are inversely related. This
means when frequency increases, wavelength decreases
(or visa versa)
Wavelength
Wavelength
Wave Characteristics
Amplitude - Displacement of the medium when the wave
moves through it. (How far the medium moves from its
equilibrium point)
• Depends on the amount of energy transferred by the
wave.
Speed - How fast the wave moves
• Depends on density of medium
• Related to the frequency and wavelength of the wave.
speed  frequency  wavelength
Wave Behavior
Reflection - Occurs when a wave bounces off a surface or
object.
• When the end of the original medium is rigid or fixed, the
reflected waves is inverted (up side down)
Original Wave
Reflected Wave
• When the end of the original medium is free to move, the
reflected waves is the same as the original wave
Original Wave
Reflected Wave
Wave Behavior
Refraction - Occurs when a wave bends as it enters or
leaves a different medium.
• Caused by a change in the speed of wave propagation
in the medium.
• Geologists use refracted and reflected seismic waves to
map rock layers under the ground’s surface and to
search for natural resources.
Diffraction - Occurs when a wave bends around a
barrier or opening.
• Caused by the wave energy spreading out in the
medium.
Wave Behavior
Interference - Occurs when two or more wave overlap or
superimpose.
• When waves overlap, their parts add together
temporally before moving past each other.
Small Wave
Bigger Wave
Small Wave
Crest
Crest
Small Wave
Crest
Small Wave
No Wave
Trough