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Interference
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Interference: The Basics
Waves can interfere with each other.
There are two different types of
interference:
Constructive
Destructive
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Constructive Interference
Makes effects greater
For Transverse Waves:
A crest will interfere with another crest
constructively to produce a larger crest and
a trough will interfere to produce a larger
trough For Longitudinal/Comressional Waves:
Compressions interfere with compressions
Rarefactions interfere with rarefactions
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Destructive Interference
Lessens the effects
For Transverse Waves
A crest will interfere with a trough to lessen
or cancel the displacement of each.
For Longitudinal/Compressional Waves
Compressions will interfere with
rarefactions to lessen or cancel the
displacement of each.
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Sound Waves
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Sound Waves
Sound is a longitudinal/compressional
wave.
Sound requires a medium.
Sound can be produced by vibrating
objects.
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Sound Waves (cont.)
Sound waves reflect. Sound produces echoes when it bounces
off hard surfaces. Sound waves interfere.
Destructive interference makes soundsquieter. Constructive interference makes
sounds louder. Sound waves reflect in tubes of some
musical instruments.
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Light Waves
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Light Waves
Light waves reflect!
The Law of Reflection says the angle of
incidence is equal to the angle of reflection. The angle of incidence is the angle betweenthe incident ray and a line perpendicular tothe surface.
The angle of reflection is the angle betweenthe reflected ray and a line perpendicular tothe surface.
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Law of Reflection
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Mirrors
Light waves reflect inplain mirrors
The image appears asfar behind the mirror asthe object is in front of it
The image and the object
appear to be the samesize
The image is upright
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Light Can Diffract
Diffraction is the bending of a wave
around a barrier or around the edges of
an opening. Waves with a longer wavelength diffract
more readily
When light waves diffract different lightpatterns can be observed
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Diffraction Grating
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Light Can Interfere
Light can interfere constructively and
destructively to produce a color pattern
Light can reflect off the bottom and topsurfaces like oil on water to produce a
color pattern
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Light can Refract
Waves refract when they change
direction upon entering another medium
in which the waves travel at differentspeeds
Light refracts when it enters a different
medium at an angle other thanperpendicular and changes speed
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Refraction
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Light Entering/Leaving a Prism
Light slows down when it
enters a prism and bends
down when it strikes it atan angle
When light exits the prism
it speeds back up andbends down again
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White Light and a Prism
When white light entersanother medium such as
a prism the colors mayspread out. This isbecause the violet endof the spectrum slows
down more than the redend and therefore bendsmore.
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Lenses
Lenses
can be
concaveor convex
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Doppler Effect
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The Doppler Effect
The Doppler Effect is an apparent
frequency shift due to the relative
motion of an observer and a wavesource.
A Doppler shift occurs when a wave
source is moving towards an observeror away from an observer.
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Doppler Effect
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The Doppler Effect
As a wave sourceapproaches an observer,the observer perceives ahigher frequency than thesource is producing.Wavelengths are shorterand the frequency is
higher in front of amoving source.
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