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1
Recognize that all waves transfer energy.
Relate frequency & wavelength to the energy of different types of electromagnetic waves & mechanical waves.
Compare and contrast the characteristics of electromagnetic and mechanical (sound)waves.
Explain the
phenomena of
reflection,
refraction,
interference, &
diffraction.
Explain the Doppler
Effect in terms of
everyday
interactions.
Relate the speed of sound to different mediums.
2
WavesWavesWaves are disturbances Waves are disturbances
that carry that carry energy energy through matter or space.through matter or space. Clip
The material does not The material does not actually travel with the actually travel with the wave….. only the energy is wave….. only the energy is carried.carried.
Waves can be visible or Waves can be visible or invisible evidence of energy invisible evidence of energy transfer.transfer.
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Types of WavesTypes of WavesTwo types of waves:
•Mechanical•Non-Mechanical
Mechanical: waves need a medium in order to travel.
Examples: Sound, water
Non-mechanical: waves do not need a medium to travel.
Examples: light, gamma waves, microwaves, x-rays
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Waves that require a medium to travel.
Light waves are NOT Mechanical Waves.
Sound and water.
Mechanical WavesMechanical Waves
A medium is the material a A medium is the material a wave travels throughwave travels through
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Ways that waves travel
•Transverse waves–Water, light
•Compressional waves–sound
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Transverse WavesTransverse WavesTransverse waves are UP &
DOWN movements.
EX: water waves, radio waves (all EM waves)
The displacement of individual particles is perpendicular (at right angles) to the direction of the wave.
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Describing a Transverse Wave
Crest
Trough
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amplitude
The higher the amplitude, the more energy the wave is carryingIn a compressional wave- it’s how tightly the compressions are.
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Frequency & WavelengthWavelengthWavelength
•Distance between to identical points on adjacent waves.•Meters•As the wavelength decreases the frequency increases
FrequencyFrequency•Number of waves per second•Hertz
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λ
Movement of a Transverse Wave911
CLIP
Example - Water
Remember: Energy is transferred ----NOT THE MATTER!--
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Compressional WavesCompressional waves are a series of PUSHES & PULLS in which the motion of the medium is in the same direction as the wave
Ex. Sound Waves
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Characteristics of a Characteristics of a Compressional WaveCompressional Wave
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Parts of a Compressional wave• Compressions &
Rarefactions
Rarefaction is a place where the Rarefaction is a place where the atmospheric pressure is lowest.atmospheric pressure is lowest.
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Speed of a waveν = f λ
•ν is the velocity (m/s)• f is the frequency (hertz)•λ is the wavelength (m)
The speed of a wave changes as it moves through different media
The speed of a mechanical waves is constant for any given medium..
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Let’s do some practice
problems.
ν = f λ
Wave Wave interactions interactions with matterwith matter
Wave interactions with matter
Reflection occurs when a wave hits another wave or object that it cannot pass through and bounces back.
17
Law of Reflection
18RefractionRefraction occurs when a wave passes from one
medium to another at an angle and bends (changes direction) due to a change
in speed.
Refraction
•Diffraction is a wave phenomenon that is dependent on wavelength
•Light waves bend as they pass by the edge of a narrow aperture or slit
Diffraction occurs when a wave passes through an
opening and spreads out
19
Diffraction
•When a wave encounters an obstacle. •Apparent bending of waves around small obstacles and the spreading out of waves past small openings.
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Constructive InterferenceConstructive Interference occurs when two or more waves hit the same point and combine to produce a larger single wave.
Destructive InterferenceDestructive Interference occurs when two or more waves hit the same point and combine to produce a smaller single wave.
Constructive InterferenceConstructive Interference
Constructive InterferenceConstructive Interference
Destructive InterferenceDestructive Interference
Clip
Recognize that all waves transfer energy.
Relate frequency & wavelength to the energy of different types of electromagnetic waves & mechanical waves.
Compare and contrast the characteristics of electromagnetic and mechanical (sound)waves.
Explain the
phenomena of
reflection,
refraction,
interference, &
diffraction.
Explain the Doppler
Effect in terms of
everyday
interactions.
Relate the speed of sound to different mediums.
2
GOALS REVISITED.