Transcript The Energy of Waves

The Energy of Waves
Section 1: The Nature of Waves
Anticipation Guide: True or
False
 Light
waves are mechanical waves
because they must travel in a medium
 In
space, no one can hear an explosion
 Water
waves are a combination of
longitudinal and transverse waves
What is a wave?
 Definition:
A wave is any disturbance that
transmits energy through matter or space.
Waves carry energy, not
matter
Waves use energy to do work on everything in its path. The waves do
work on the water to make it move up and down as well as work on the
leaf so it bobs up and down with the water.
Energy transfer through a
medium
a
wave can be described as a disturbance
that travels through a medium,
transporting energy from one location to
another location.
 The medium is simply the material through
which the disturbance is moving; it can be
thought of as a series of interacting
particles.
Mechanical waves
require a medium
 Sound
waves require a medium
 Ocean waves require a medium
 Waves on a string instrument require a
medium
A
mechanical wave is a wave which is
not capable of transmitting its energy
through a vacuum. In other words, it
requires a medium
An example of a mechanical
wave
Energy transfer without a
medium
 Electromagnetic
waves are waves that do
not require a medium to transmit energy
 Examples of these are microwaves, TV, xrays, and radio signals
 While these types of waves can travel
through a medium, they travel faster
through empty space
Example of an electromagnetic
wave
Waves in the electromagnetic spectrum vary in size from very long radio waves the
size of buildings, to very short gamma-rays smaller than the size of the
nucleus of an atom.
Types of Waves
 Waves
can be classified based on the
direction that the particles of the medium
vibrate compared to the direction in which
the waves travel.
 The two main types of these waves are
transverse and longitudinal. If found in
combination is called a surface wave.
Types of Waves: Transverse
 Transverse
waves have particles that
vibrate in an up and down motion moving
the waves across in a perpendicular
manner to which the wave is traveling
 Remember that perpendicular means to
be at right angles
 A rope is an example of a transverse
wave.
Types of Waves: Transverse
Types of Waves: Transverse
Demonstration
Types of Waves: Longitudinal
A
longitudinal wave has particles that
vibrate back and forth along the same path
that the wave travels.
A
spring (or slinky) is an example of a
longitudinal wave
Types of Waves: Longitudinal
 Compression
is when the spring is
(particles are) tightly pushed together
 Refraction
is when the coils (particles) are
spread farther apart.
A
sound wave is an example.
Types of Waves: Longitudinal
Demonstration
Types of Waves: Combination
 When
waves occur at or near the
boundary between two media (air and
water for example) transverse wave and a
longitudinal wave can combine to form a
surface wave.
 Surface
waves look like transverse waves
but the particles in the medium move in
circles rather than up and down.
Types of Waves: Combination
Particles move
forward at the
crest and
backward in the
trough.
Anticipation Guide:
True or False
electromagnetic
 Light
False
waves are mechanical
waves
X
because they must travel in a medium
 In
space, no one can hear an explosion
True
Sound waves require a medium
 Water
True
waves are a combination of
longitudinal and transverse waves
Also called surface waves.