A surfer takes advantage of a wave’s
energy to catch an exciting ride
The ocean wave that this surfer is
riding is just one type of wave
Besides water waves, waves are also
responsible for light, sound, and
even earthquakes
From music to television, waves
play an important role in your life
every day
We will learn about the properties
of waves and how waves interact
with each other and everything
around them.
A wave is any disturbance that
transmits energy through matter or
space
Examples of waves:
– Water waves in the ocean
– Microwaves inside the microwave oven
– Light waves from the sun
– Radio waves transmitted to the radio
– Sound waves from the radio, telephone
and voices
Energy can be carried away from its
source by a wave
The material through which the wave
travels does not move with the energy
Sound waves often travel through air,
but the air does not travel with the
sound
If air were to travel with sound, you
would feel a rush of air every time you
heard the phone ring.
Some waves transfer energy by the
vibration of particles in a medium
A medium is a substance through
which a wave can travel
A medium can be a solid, a liquid, or
a gas
When a particle vibrates, it can pass
its energy to a particle next to it
As a result, the second particle will
vibrate in a way similar to the first
particle
In this way, energy is transmitted
through a medium
Sound waves require a medium
Sound energy travels by the
vibration of particles in liquids,
solids, and gases
If there are no
particles to vibrate,
no sound is possible
Other waves that require a medium
include ocean waves, which travel
through water, and seismic waves
that travel through the ground
Waves that require a
medium are called
mechanical waves
Some waves can transfer
energy without traveling
through a medium
Visible light is an example
of a wave that doesn’t
require a medium
Other examples are
microwaves produced by
microwave ovens, TV and
radio signals, and X rays
used by dentists and doctors
Waves that do not require a medium
are called electromagnetic waves.
Although electromagnetic waves do
not require a medium, they can
travel through substances such as
air, water, and glass
Light from the sun is a type of
electromagnetic wave
Light waves from some stars and galaxies
travel distances so great that they can only
be expressed in light years.
A light year is the distance that light travels
in a year.
Some of the light waves from these stars
have traveled billions of light years before
reaching Earth.
This means that the light that we see today
from some distant stars left the star’s
surface before the Earth was formed.
Waves can be classified based on the
direction in which the particles of
the medium vibrate compared with
the direction in which the waves
travel.
The two main types of waves are
transverse waves and longitudinal
waves.
Waves in which the particles vibrate
with an up-and-down motion are
called transverse waves.
The particles in a transverse wave
move across, or perpendicular to ,
the direction that the wave is
traveling.
The highest point of a transverse wave is
called a crest
The lowest point between each crest is
called a trough
In a longitudinal wave, the particles of
the medium vibrate back and forth
along the path that the wave travels.
A section of a longitudinal wave where the
particles are crowded together is called a
compression
A section where the particles are less
crowded than normal is called a rarefaction
Compressions and rarefactions travel along a
longitudinal wave much in the way the
crests and troughs of a transverse wave
move from one end to the other
A sound wave is an example of a longitudinal
wave
Sound waves travel by compressions and
rarefactions of air particles.