What are waves?
Learning Targets
To show how waves transfer energy.
To be able to illustrate or show how
vibrations in materials may produce
waves that spread away from the
source in all directions.
Wave
Definition: A disturbance that transfers
energy from place to place.
What carries waves? A medium, a
medium is the material through which a
wave travels.
A medium can be a gas, liquid, or solid.
The water waves below are carrying energy but
are not moving. Waves can only exist as they
have energy to carry.
Waves transfer energy, not matter.
Not all waves require a
medium to travel.
Light from the sun travels through
empty space.
What causes waves?
Waves are created
when a source of
energy causes a
medium to vibrate.
A vibration is a
repeated back and
forth or up and
down motion.
Types of waves: Waves are
classified according to how
they move.
Longitudinal Waves or
Compression Wave
In a longitudinal wave the matter in the wave moves
back and forth parallel to the direction of the wave.
This is the seismic wave of an earthquake.
Bite Size Physics
Try the Slinky Wave
Jerk the slinky forward
The beginning of the slinky moves away from
its equilibrium position and then back.
The disturbance continues down the slinky.
if we keep “pulsing” the slinky back and forth,
we could get a repeating disturbance.
Slinky Wave
It would look like this.
This is a longitudinal wave.
Watch the energy being transferred.
Transverse Waves
In a transverse wave the matter in the wave moves
up and down at a right angle to the direction of the
wave. This is the wave of aftershocks.
Bite Size Physics
Compression wave
How the energy in
transferred in a
compression wave?
Sound Waves
Sound travels as vibrations moving through
the air as a compressional wave.
Sound travels through air, but travels through
other materials as well. Whale communicate
through long distances by producing sounds
under water.
HSP Science Grade 5: How Sound Reaches You
Sound Waves
Sound waves are compressional waves.
When a noise is made, such as when a
locker door slams shut and vibrates,
nearby air molecules are pushed
together by the vibrations.
When a sound wave reaches your ear, it
causes your eardrum to vibrate. Your
inner ear then sends signals to your
brain, and your brain interprets the
signals as sound.
Sound Travels Through Different Media
We hear sound which usually
travels through air. Sound
travels through other media
as well, such as water and
various solids.
Sound travels at different
speeds in different media.
Sound typically travels faster
in a solid than a liquid and
faster in a liquid than a gas.
HSP Science Grade 5: How
Sound Reaches You
Seismic Waves
An energy wave which vibrates through the
earth’s crust as the crust bends or breaks.
Seismic waves are exist as both transverse
and compressional waves.
The earthquake is the compressional wave
The aftershocks are the transverse waves
Some travel through the earth and some
travel across the earth’s surface.
Seismic Wave in Earthquake
Animation of an Earthquake
http://www.pbs.org/wnet/savageearth/
animations/earthquakes/main.html
Earthquake Wave
Aftershock Wave
Combinations of waves
Surface waves are a
combination of
transverse and
longitudinal
waves.The waves
occur at the surface
between water and
air.
Waves and Energy
Because it is moving, the falling pebble has
energy.
As it splashes into the pool, the pebble
transfers some of its energy to nearby water
molecules, causing them to move.
What you see is energy traveling in the form
of a wave on the surface of the water.
Waves and Energy
The waves don’t even carry the water along
with them. Only the energy carried by the
waves moves forward.
All waves have this property—they carry
energy without transporting matter from
place to place.
A wave will travel only as long as it has
energy to carry.
Flow of Energy in a Wave
Observe how energy can flow along the
wave.
Amplitude
Height of the wave
Higher the amplitude, higher the wave
The more the particle moves, the more work
is being done
The more work there is, the more energy
Sound—higher the amplitude, louder the
sound
Seismic—higher the amplitude, stronger the
earthquake
Speed
Waves in different
mediums travel at
different speeds.
However, in a
given medium and
under the same
conditions the
speed of the wave
is constant.
Wave Websites
Showing the different types of waves:
http://web.ics.purdue.edu/~braile/edumod/w
aves/WaveDemo.htm#P_S_R_L_Animations
Earthquake seismic waves:
http://www.pbs.org/wnet/savageearth/anima
tions/index.html
Teacher Tube—Waves and Sound:
http://www.teachertube.com/members/viewV
ideo.php?video_id=129340&title=podcast_4_
1___intro_to_waves_and_sound
United Streaming
Faults, Seismic Waves, and Earthquakes
video segment
Sound Waves video segment
Demonstration
Dominos
Place 20 close together
Place 20 further apart
Teacher Tube
The Wave
What are Waves?
A way to move energy from place
to place!