What are
waves?
Wave
Definition: A disturbance that transfers
energy from place to place.
What carries waves? A medium, a
medium is the material through which a
wave travels.
A medium can be a gas, liquid, or solid.
Not all waves require a
medium to travel.
Light from the sun travels through
empty space.
What causes 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.
Types of waves: Waves are
classified according to how
they move.
Transverse wave
Waves that move the
medium at right angles
to the direction in which
the waves are traveling
is called a transverse
wave.
Transverse means
across.The highest
parts are called crests
the lowest parts are
called troughs.
Compressional Wave
Matter vibrates in
the same direction
as the wave travels.
Example: Slinky
Compressional wave
The parts,where the
coils are close
together are called
compressions, the
parts where the coils
are spread out are
called rarefactions.
Combinations of waves
Surface waves are a
combination of
transverse and
longitudinal
waves.The waves
occur at the surface
between water and
air.
Properties of Waves
Basic Properties of Waves
Amplitude
Wavelength
Frequency
Speed
Draw Transverse wave and
label: crest & trough
the old Slinky song)
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.