What are waves?
wave is a disturbance that carries
energy through matter and space.
 The matter through which waves
move through is called a MEDIUM. It
can be a solid, liquid or gas.
Mechanical Waves
 Waves
that require a medium are called
mechanical waves.
 Nearly all waves are mechanical waves.
Ex: ocean waves, sound waves and seismic waves (earthquakes)
 Electromagnetic
Waves are NOT
mechanical waves, so they do not need a
medium to travel through!
Energy moving through a medium
•The picture above shows a medium made up of
particles connected by springs.
• As one individual particle is disturbed, it transfers
the energy from that particle to the next and so on.
• So… energy is transported from one end of the
medium to the other end of the medium without
transporting any actual matter!
•Ex: Like being in the ocean and a wave picks you up and
puts you down as it passes by.
•Or Dominoes falling into each other
How mechanical waves move
through matter…
 The
kind of medium, (solid, liquid, gas)
determines the mechanical wave speed.
 Waves rely on the elasticity and inertia
properties of the medium. Basically how
are the particles moving in the medium?
 Which medium do mechanical waves
travel faster in, solids, liquids or gases?
(*hint* think about molecules)
How mechanical waves move
through matter…
 Solid
in solids and liquids the molecules are more closely
packed together than gases, so energy is transferred
from one particle to another particle faster.
So which medium do mechanical waves travel through
the slowest?
Gases! Because…
the particles are moving rapidly and randomly it is
hard for the particles to transfer the energy to one
Faster than the Speed of
 In
the air, sound will generally travel
300 meters per second.
 In the liquids, sound will generally
travel 1500 meters per second.
 In the solids, sound will generally
travel 2500 meters per second.
Breaking the Sound Barrier
Motion of molecules in a
mechanical wave
Think of a wave
created by fans in a
baseball stadium and
how the molecules
move in a set pattern.
 Molecules dealing with
kinetic energy, have
random motion, like
gases. Less energy is
Uses of Mechanical waves
 Ultrasound
 Testing buildings and structures for
 Geologists use mechanical waves to
detect the epicenter of earthquakes
and to explore the earth’s crust and
What are epicenters?
Epicenter is the
point on the Earth’s
surface where an
earthquakes starts.
 Focus is the point
in the earth where
an earth quake
Detecting the Epicenters
Very Dense Layer
Ultrasound Picture
New 3D Ultrasound Picture
Using waves to detect defects in
man-made structures.
Break in the rail line