Wave
Properties
Six Interactions of Waves
Wave Properties
There are 6 main properties, or interactions, of
waves that occur when a wave comes in contact
with another wave , or a boundary.
The 6 Interactions of waves are






Interference
Diffraction
Reflection
Refraction
Absorption
Polarization
Interference
When two or more waves
combine together.
Superposition principle
 There
are typically many waves in the same
system at the same time.
 When more than one wave is present, the
total oscillation of any point is the sum of the
oscillations from each individual wave.
 The sound waves and light waves you
experience are the superposition (adding up)
of thousands of waves with different
frequencies and amplitudes.
 Your eyes, ears, and brain separate the
waves in order to recognize individual sounds
and colors.
Constructive Interference
Constructive
interference occurs when waves
add up to create a larger amplitude wave.
These
waves are in-phase with each other.
Constructive Interference
When two waves combine to make a larger wave.
(crest & crest) or (trough & trough)
Destructive Interference
 Destructive
interference occurs when waves
add up to make a smaller amplitude wave.
 These
other.
waves are out-of-phase with each
Destructive Interference
 Two
or more waves combine to produce a smaller
wave or destroy the wave completely.
(crest & trough)
Check for Understanding!
1.
2.
Results of Interference of Waves
 One
of the consequences of wave interference is a
phenomenon called resonance.
 Resonance
is the reinforcing of an object’s natural
frequency so that the amplitude increases very
quickly.
 Can
you think of something that you have seen or
heard that you believe to be caused by
resonance?
Standing Waves

A wave that is confined
between boundaries is
called a standing wave.

With all waves, resonance
and natural frequency
are dependent on
reflections from
boundaries of the system
containing the wave.

Resonance occurs when
the reflected pulses add
together to form a large
amplitude pulse.
Resonance
Resonance
can also occur when one
object vibrates another without
touching
A
sound wave vibrates a snare drum
 A singer hits a note that shatters a glass
 A struck tuning fork causes another
tuning fork of the same frequency to
vibrate
 The strings of a guitar vibrate from a
sound across the room
Resonance
Natural Frequency and Resonance
The
natural frequency is sometimes called the
resonant frequency because the frequencies are the
same when the large amplitudes begin to occur.
Resonance
Real World Examples:
Chinook Helicopter Ground Resonance Test
The Tacoma-Narrows Bridge is an example
of driven oscillations that result in large
amplitude oscillations.
Diffraction
The bending of
a wave as it
moves around
an obstacle or
passes through
a narrow
opening.
Diffraction
 When
waves pass a barrier they curve around it
slightly.
 When
they pass through a small opening, they
spread out almost as if they had come from a
point source.
 These
effects happen for all types of wave:
water; sound; light; seismic waves, etc.
Diffraction
Diffraction & Bats
•Bats hunt by echolocation—bouncing sound waves
off of prey and listening for echoes, so they need to
emit sound with a wavelength smaller than the
typical moth.
•Bats use ultrasonic sound waves (high frequency
waves humans can’t hear) to hunt moths.
•The bats use ultrasound is because at lower
frequencies the longer waves would diffract around
the moth because they would be close to the same
size.
•High frequency sound waves reflect off the moths
rather than diffracting around them.
Reflection
 Reflection
is a property of waves that allows a
wave to completely bounce off of the surface of
a new medium.
 The
Law of Reflection states that the angle of
incidence is always equal to the angle of
reflection.
A
ray of light heading towards an object is
called an incident ray. If it reflects off the object,
it is called a reflected ray.
Law of Reflection
θi
θr
θi = θr
Reflection
 Humans
 Light
see light by reflection.
reflects off of objects and into our eyes.
Refraction
 Refraction
is the property of a wave where the
wave changes direction (bends) when it enters a
new medium.
Refraction
 Refracted
waves speed up or slow down when
entering a new medium.
Sound Waves
change
direction in
different air
temperatures.
Examples of
Refraction
of Light
Polarization
 Polarization
is a property of waves that allows
a wave to oscillate with more than one
orientation (direction). Because of this, one
direction can be blocked out.
 Polarization cannot occur with sound waves in
liquids or gases because longitudinal waves
travel parallel to the wave direction.
 Transverse waves are the best example of
polarization.
Polarization
 Electromagnetic
Waves are an example of
transverse waves that travel in more than one
direction.
Polarization
A
polarized wave has had one or more
directions blocked out by something called a
polarizer.
Polarization
A
polarized wave has had one or more
directions blocked out by something called a
polarizer.
Polarization
 This
is how sunglasses work!
Absorption
 Absorption
of waves is the transfer of the
energy of a wave to matter as the wave passes
through it.
Absorption
 All
types of waves can be absorbed.
Absorption
 We
feel heat due to the absorption of most
wavelengths of Electromagnetic Radiation from
the Sun.