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The Energy of
Waves
Waves
General and Electromagnetic
Nature of Waves
Waves are disturbances
that transfer energy from place to
place.
Energy can be carried away from its
source by a wave, but the medium
does not move with the energy.
Wave Travel
As waves move through media
(such as a solid, liquid or gases) it
performs work by transferring
energy from one particle (atom)
to another.
Sound waves transfer energy by
vibration of particles in a medium.
Sound Waves
Require a medium
to travel
– they vibrate particles.
Waves that require a medium are called
mechanical waves.
Space is not a media (void of Matter)–
therefore we cannot hear the explosion of a
super nova – we can only see it.
Electromagnetic Waves
An
Electromagnetic
Wave is a wave
that can travel
through empty
space or matter and
is produced by
charged particles
that are in
motion.
Forces
All Matter (Atoms - Protons & Electrons)
exert positive and negative charges
creating an Electrical Field.
Thus - this Electric Field (E) exerts a force
on all other charged particles that are in a
field.
Forces
The electromagnetic wave is made of two
parts—an electric field and a magnetic
field. These fields are force fields.
A force field enables an object to exert
forces on other objects, even though they
are
not touching.
Forces - Magnetic
Just as gravitational field
exerts a force on a
mass, a magnetic field
exerts a force on
another magnet and on
magnetic materials.
Magnetic fields cause
other magnets to line
up along the direction
of the magnetic field
Earthquakes
3 Types of Mechanical Waves
Primary waves (P Waves)
Cause particles in rocks to move back and
forth in the same direction that the wave
is
traveling.
3 Types of Mechanical Waves
Secondary Waves (S – Waves)
Causes particles in rocks to move at right
angles to
the direction
of the wave
travel.
3 Types of Mechanical Waves
Surface Waves
Causes rock particles in a backward, rolling
motion and
side-to-side,
swaying
motion.
Waves
Waves carry energy & information
WAVES
DO NOT
CARRY
THE
MEDIUM!!!
Wave Energy can
provide information
such as:
 Sound
 Color
 Pictures
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Radio waves – tv
Microwave – cell
phones
Wavelength ( )Lambda:
The length of one complete cycle of a
wave is from crest to crest or trough to
trough.
Amplitude
How high the wave rises above, or falls
below, the normal level is called the wave’s
amplitude.
The amplitude of a transverse wave is onehalf the distance between a crest and a
trough
Higher the wave –
the greater the
energy.
Frequency
How many waves pass
in 1 sec.
The faster the vibration
is, the higher the
frequency is of the
wave that is produced.
Measured Unit in hertz
(Hz)
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How fast the wave can
transfer energy.
How fast the wave can
transfer energy.
v=fx
v = speed (velocity)
Units=m/s
f = frequency
Units=Hz
 = wavelength
Units=m
Wave Speed
Longitudinal Waves
Also called Compressional Waves
requires a Media
Wave and energy
are in same
direction
Ex: Slinky
 The compression
will move along
the slinky forward
and then back.
 Sound

Longitudinal Wave Parts
Compression-The condensed portion
 Rarefaction-The separated part of
the wave.
 Wavelength-distance from
compression to compression

Do not require a Medium
Visible Light does not require media.
They are Electromagnetic Waves.
Examples: microwaves, X-Rays, TV and
radio waves.
Natural Waves:
Even though electromagnetic waves do not
require a media they can travel through
space, air, water, and glass.
Electromagnetic Waves
Sun light travels through space, air and water
to warm our planet and sustain life.
Electromagnetic waves travels fastest
through space.
the speed of light = 299 792 458 m / s usually
stated as 300, 000 km/s
or 983,571,056 feet per second
Electromagnetic Waves
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.
Electromagnetic Wave
All electromagnetic radiation has
fundamental properties and behaves in
predictable ways according to the basics
of wave theory.
Electromagnetic radiation consists of an
electrical field (E) which varies in
magnitude in a direction perpendicular to
the direction in which the radiation is
traveling, and a magnetic field (M)
oriented at right angles to the electrical
field. Both fields travel at the speed of
light (c).
Electromagnetic Radiation
Transverse Waves
Wave and energy move perpendicular
to each other. (90 degrees)
The wave travels to the right as the
oscillation points move up and down.
Transverse Waves
Energy moves left to right as
waves moves up & down
Ex: water waves
A Rope that is
moved up
and down
Light
Transverse Waves
TRANSVERSE WAVES!!!!
All travel at the same speed
The difference is in the frequency and the
wavelength.
If one goes up, the other goes down.
Parts of A Transverse Wave
Crests: high point of the wave
Troughs: low point of the wave
Parts of the EM Spectrum
Radio WavesLongest
wavelength,
lowest energy,
lowest frequency.
 Used for TV’s,
Radios and Cell
Phones
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Example: Radio Waves - Echolocation
Radar:
RAdio Detecting and
Ranging
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Radar first used In WWII
Echolocation is used by
bats, dolphins and
many whales
Microwaves
A form of radio waves-some books place
them separately and some put them in
with radio.
They are the highest frequency (most
energy) of the radio waves.
Infrared (IR)
Heat
Used to find people
in the woods.
Infrared film detects
how hot something
is.
Used to detect
cancer
Beneath red
Visible Light
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ROY G. BIV-colors
of visible light.
Sunlight emits UV
along with other
rays.
Vitamin D
Too much harmful.
Mostly filtered by
ozone.
Red is longest
wavelength
Visible Light
Ultraviolet Radiation
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Main source is
sunlight
Helps your body
produce vitamin D
Overexposure =
burns and skin cancer
Sunscreen helps to
block
Beyond violet
X-rays and Gamma Rays
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X-rays-See bones.
High Energy
Use lead to block!
Gamma rays-highest
energy
Used to treat cancer
Generated by
radioactive atoms
Wave Interactions
 Interaction
-Waves run into other
objects or another wave
 Interaction can increase or decrease
wave energy
 Interaction can change the properties
of the wave
 Interaction can change the direction
Reflection
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A wave bouncing off
of a surface
 Mirror
 Wave hitting a wall
Incident wave –
moving to surface
Reflected wave –
moving away from
surface
Reflection
Reflection
Refraction
Bending of wave as it
changes speed
 Speed changes from on
medium to another
 Air to water
 Water to oil
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Refraction
Refraction
Diffraction
Bending of a wave when it comes
into contact with the edge of
another object
Light bending around a door
Diffraction – Sound Waves
Interference
The result of two or more waves
overlapping each other.
When sound waves from several
instruments combine the wave produces a
higher amplitude thus a louder sound
Interference
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The effect of 2 or more
waves interacting
Can be constructive or
destructive
Constructive Interference
Wave crest come together at the same
location.
Waves join together to make a
larger
wave.
Constructive Waves
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Increased Amplitude
Destructive Interference
The crest of one wave meets the trough
of another wave
Crest and trough subtract from each
other to make a smaller wave
Sometimes
the
interference
cancels both
waves
Destructive Wave
Decreased Amplitude
Standing Wave
Is a wave that forms a stationary
pattern in which portions of the
wave are at the rest position due
to total destructive interference
and other portions have a large
amplitude due to constructive
interference.
Standing Wave
Resonance
All objects have a frequency or set of
frequencies with which they naturally resonate
when struck, plucked, strummed or somehow
disturbed. Each of the natural frequencies at
which an object vibrates is associated with a
standing wave pattern. When an object is forced
into resonance vibrations at one of its natural
frequencies, it vibrates in a manner such that a
standing wave is formed within the object. So
the natural frequencies of an object are merely
the harmonic frequencies at which standing
wave patterns are established within the object.
Resonance
Doppler
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Sound
Change in
frequency and
pitch of a sound
that is caused
by either the
movement of
the source or
the listener
Ambulance
Race car
Effect