Transcript Waves PowerPoint File

How does one
differentiate
between
transverse and
longitudinal
waves?
7.11.6
Wave
Waves are a disturbance that transfers
energy from place to place.
Waves can be Transverse, Longitudinal
(Compressional), or Electromagnetic.
Types of waves: Waves are
classified according to how
they move.
Mechanical 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.
Mechanical Waves
Can be transverse or longitudinal.
All mechanical waves need a material
medium to shake vibrate.
The wave medium is not the wave and it
doesn't make the wave; it merely carries
or transports the wave from its source
to other locations.
A medium can be a gas, liquid, or solid.
What type of mechanical
wave is this?
Transverse wave
Transverse means across.The
highest parts are called crests the
lowest parts are called troughs.
A wave in which the motion of the
medium is perpendicular to the
motion of the wave.
The motion of the medium is up
and down. The motion of the wave
is right or left.
This movement creates right
angles to the direction in which the
waves are traveling.
Example: Seismic Secondary (S)
waves
What type of mechanical wave is
this?
Compressional Wave
Matter vibrates in the same
direction as the wave
travels.
The motion of the medium
is left or right.
The motion of the wave is
left or right.
Sound waves are
longitudinal. The air
vibrates back and forth
along the same direction as
the wave is traveling.
Example: Slinky
Compressional /Longitudinal Wave
Rarefactions,
where the parts of
the medium are
farther apart than
normal (troughs).
Compressions,
where the parts of
the medium (coils
of the Slinky) are
closer together than
normal (crests).
Points A, B, and C create a
_______.
The straight line that runs from A
to G is called what?
C, D, and E form what part of the
wave?
Electromagnetic
Waves
Not all waves require a
medium to travel.
Light from the sun travels through
empty space.
Electromagnetic Waves
EM waves are transverse waves
consisting of changing electric fields and
magnetic fields.
EM waves do not require a medium.
They travel through a vacuum, or empty
space, as well as through matter.
This is called electromagnetic radiation.
Electromagnetic radiation behaves like a
wave and like a particle.
How are EM waves produced?
Electric Field
Exerts electric force on charged particles.
They can be produce by changing magnetic
fields
Magnetic Field
Exerts magnetic forces and can be produced
by changing electric fields.
Electromagnetic waves are produced when
an electric charge vibrates or accelerates.
In other words it is produced in constantly
changing fields.
How do they travel?
The fields regenerate each other.
The magnetic and electric fields of an
electromagnetic wave are perpendicular to
each other and to the direction of the wave.
http://www.walter-fendt.de/ph14e/emwave.htm
z
y
Magnetic Field
Electric Field
x
Electromagnetic Waves
There are different types of electromagnetic
waves
Radio waves
Infrared waves
Visible light waves
Ultraviolet light waves
X-rays
Gamma rays
These waves can travel through air, through the
walls of your house, and even to your TV and
radio.
Properties of Waves
Basic Properties of Waves
Amplitude
Wavelength
Frequency
Speed
Draw Transverse wave and
label: crest & trough
Draw a Compressional wave:
label compression& rarefaction
Amplitude
Amplitude is the maximum distance the particles of the
medium carrying the wave move away from their rest
positions.
The farther the medium moves as it vibrates the larger the
amplitude of the resulting waves. The greater the
amplitude the greater the amount of energy
Amplitude of transverse waves
The amplitude of a transverse wave is
the maximum distance the medium
moves up or down from its rest
position. You can find the amplitude of
a transverse wave by measuring the
distance from rest to crest or rest to
trough.
Amplitude of a longitudinal
wave.
The amplitude of a longitudinal wave is
a measure of how compressed or
rarefied the medium becomes.
Wavelength
A wave travels a certain distance before
it starts to repeat. The distance
between two corresponding parts of a
wave is its wavelength.
Transverse measure from crest to crest
or trough to trough.
Longitudinal measure from one
compression to the next.
Frequency
The number of complete waves that
pass a given point in a certain amount
of time.
AKA number of vibrations per second.
Frequency measured in hertz (Hz).
Speed
The speed, wavelength, and frequency
of a wave are related to each other by a
mathematical formula.
Speed = wavelength x frequency
Frequency = speed/wavelength
Wavelength = speed/frequency
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.
Chapter 15 -3
Ways Waves Interact
Reflection
Refraction
Diffraction
Interference
Constructive
Destructive
Standing Waves
Reflection
When an object or
wave hits a surface
through which it
cannot pass, it
bounces back.
Angle of incidence
Angle of reflection
Examples of reflection
Mirror
Echo
Ball against a wall
Refraction is when a wave
moves from one medium into
another medium at an angle,
it changes speed as it enters
the second medium which
causes it to bend. The
bending of waves due to a
change in speed is called
refraction.
Refraction
Though all waves
change speed when
they enter a new
medium. Bending
occurs when one
side of the wave
enters the new
medium before the
other side
Diffraction
When a wave passes a barrier or moves
through a hole in a barrier it bends and
spreads out.
Interference
Constructive interference occurs
whenever two waves combine to make
a wave with a larger amplitude.
Destructive interference when the
amplitudes of two waves combine
producing a smaller amplitude.
Standing waves:
If the incoming wave and the reflected
wave combine at the right places the
combined wave appears to be standing
still.
It appears to be standing in one place,
even though it is two waves interfering
as they pass through each other.
Nodes and Antinodes
Nodes: at certain
points, destructive
interference causes
the two waves to
combine and
produce an
amplitude of zero.
Antinodes are the
points of maximum
energy. The crests
and troughs of a
standing wave.
Resonance
Most objects have a natural frequency of
vibration. Resonance occurs when vibrations
traveling through an object match the object’s
natural frequency.
An object that is vibrating at its natural frequency
absorbs energy from the objects that vibrate at
the same frequency. Occurs in music.