Transcript Document

MT 5 LT 2 – Behavior Of
Waves
Let’s Review LT 1 –
Basic Properties of Transverse
Waves
Amplitude
Wavelength
Frequency
Speed
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Amplitude
Amplitude is the distance from the rest to crest or
rest to trough.
Farther medium moves as it vibrates, larger the
amplitude.
Greater the amplitude, greater the amount of
energy
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Wavelength
Wave travels certain distance before it
starts to repeat.
Distance between 2 corresponding parts
of a wave .
Transverse
measure from crest to crest or trough to
trough.
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Properties of
Longitudinal/Compressional
Waves
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Longitudinal Wave
The motion of the
medium vibrates in
the same direction
(parallel) as the
wave travels.
Example: Slinky
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Longitudinal Wave
Compressions:
The parts where the
coils are close
together
Rarefactions
the parts where the
coils are spread out
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Amplitude of a longitudinal
wave.
The amplitude of a longitudinal wave is
a measure of how compressed or
rarefied the medium becomes.
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Wavelength
Distance between 2 corresponding parts
of a wave.
Longitudinal measure from one
compression to the next.
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LT 2 - Wave Behaviors
HOW DO WAVES INTERACT?
Wave Behaviors
WHAT HAPPENS WHEN…
•
•
•
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A WAVE MEETS A HARD SURFACE LIKE A WALL?
A WAVE ENTERS A NEW MEDIUM?
A WAVE MOVES AROUND AN OBSTACLE?
A WAVE MEETS ANOTHER WAVE?
Wave Behaviors
HOW DO WAVES INTERACT?
Ways Waves Interact
Reflection
Refraction
Diffraction
Interference
Constructive
Destructive
• Doppler Effect
• Polarization
Reflection
pg 508
• What happens when a wave hits a wall or
some other fixed object?
• To find out, tie a rope to the back of a
chair. Gently shake the rope up and down
once to send a single pulse along the
rope as shown. Observe what happens
when the pulse hits the chair.
Reflection
• Video: Click Here
• Definition:
• If reflection occurs at a fixed boundary, the
reflected wave will be upside down
compared to the original wave.
• This happens because the wave hits a
fixed barrier and bounces off of it
Reflection
Important:
In Reflection wave
hits a FIXED barrier
and cannot pass
Real Life:
Basketball off
backboard
Related Items:
mirror
Frequency, angle
Fixed boundary=flipped
reflection
Sound would echo
Refraction
pg 509
Video: Click Here
Definition:
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.
Refraction
Ex: Pencil: half in
water, half in air
and it looks bent
Refraction
Important:
Wave must enter
NEW medium at an
angle-wave changes
speed
Real Life:
Hard to spear a fish
Related Items:
Wavelengths travel
at different speeds in
different substances
medium-air vs water
wave speed
Reflection v Refraction
Reflection’s barrier is not moving, it is
fixed as wave hits it
(The wave can’t pass through it)
Refraction: wave bends as it continues
into a new medium; speed also
changes.
Diffraction
pg 510
Video: Click Here
Definition: When a wave passes a
barrier or moves through a hole in a
barrier it bends and spreads out.
Diffraction
Important:
Wavelength
determines
diffraction as well as
gap size.
Long wavelength=long diffraction:
bends and spreads out a lot
Short wavelength=short diffraction:
slightly bends
Real Life Connection:
Waves that travel
around a log or move
through a gap
Related Items:
Wave speed
Bend
barrier
Interference – Constructive &
Destructive
Video: Click Here
Constructive Interference
pg 511
Definition: Constructive interference
occurs whenever two waves combine to
make a wave with a larger amplitude.
Constructive Interference
Important:
Constructive waves
build on each other
Real life Connection:
Rouge waves
Related Items:
Amplitude increases
Bigger wave
Destructive Interference
pg 511
Definition: Destructive interference
when the amplitudes of two waves
combine producing a smaller amplitude.
Destructive Interference
Important:
Destructive waves
can cancel each
other
Real life Connection:
Muffler on a car
Related Items:
Amplitude decreases
smaller wave
Doppler Effect
pg 516
Video: Click Here
Definition: Change in pitch of a sound source due
to the relative motion of the source and the
observer.
Observed when a police car, w/sirens blaring, passes
you, traveling in the opposite direction, at a high
speed.
Doppler Effect
It is about pitch, NOT loudness.
As something gets closer, it has a higher pitch
As it passes you, the pitch gets lower
Doppler Effect
Important:
Long Wavelength
creates a low
frequency/pitch –
after car passes you
Small Wavelength
creates a high
frequency/pitch – as
car approaches you
Real Life:
Can’t hear oncoming
cars
Related Items:
Faster the object
moves, the closer in
front and farther in
back the waves get
Polarization
pg 548-549
Video: Click Here
Definition: (ONLY with Transverse waves)
Transverse waves can travel in all directions. If it is
linearly polarized (made to go through a filter), then
the transverse vibrations in the wave are all in the
same direction.
Light is frequently used as an example of polarization.
Polarization
Important:
Unpolarized light –
vibrates in all
directions
Polarized light –
vibrates in one
direction
Real Life:
Polarized Sunglasses
Related Items:
Plane-flat surface
Light waves that
travel in all directions
You should have….
a. If reflection occurs at a fixed boundary, the reflected wave
will be upside down compared to the original wave.
b. Refraction occurs when a wave enters a new medium at an
angle because one side of a wave front moves more slowly than
the other side.
c. The larger the wavelength is compared to the size of an
opening or obstacle, the more a wave diffracts.
d. The types of interference are constructive and destructive
interference.
Take a few minutes and fill this out…..
Polarization
Important:
Unpolarized light
vibrates in all
directions.
Polarized light has
been filtered and
only vibrates in one
plane
Real Life:
Sunglasses
Related Items:
Plane-flat surface
Light waves-all
directions