l03 - reflection, refraction, diffraction ppt
TRANSCRIPT
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ObjectivesRecognize and describe the properties of:
� Wave reflection
� Wave refraction
� Wave diffraction� Wave diffraction
Each of these is a Big IdeaBig Idea
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Wave Reflection
Where have you experienced waves reflecting?
� Echoes
� Radio wavesRadio waves
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Wave Reflection
� Waves at right angles
�Waves at oblique angles
�Waves at oblique angles
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Wave Reflection
Angle of Incidence
Incident Ray
Angle of Incidence
Angle of
Reflection
Reflected Ray
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Wave Refraction
Where do waves move from one medium to another?
� Sound from cold air to warm air� Sound from cold air to warm air
� Light from space to air
� Light from air to water
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Wave Refraction� Water passes from deep water to shallow water -
Wavelength shortens
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Wave Refraction
When waves move from one medium to another, two things happen:
1. The wave velocity changes1. The wave velocity changes
2. The wave direction changes
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Wave Refraction
� Recall the universal wave equation:v = f * λ
In Medium 1 - f1=v1/λ1In Medium 1 - f1=v1/λ1
In Medium 2 -
� No matter what the medium the frequency doesn’t change:
f1 = f2
� Therefore we get:v1/λ1 = v2/λ2
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Wave RefractionSpeed of Sound:
� Sound wave speed changes depending on air temperature
v = 331m/s + (0.59 * T)vSOUND = 331m/s + (0.59 * T)vSOUND ~ 330m/s
� Does sound move faster or slower in cold air?
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Wave Refraction� Oblique waves bend
towards the normal when entering slower medium
Normal
Normal
� Oblique waves bend away from the normal when entering faster medium
� Oblique waves bend away from the normal when entering faster medium
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Wave RefractionWhen waves enter shallow water (lower speed medium)
they bend towards the normal (become more parallel to shore)
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Wave Diffraction
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Wave Diffraction
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Wave Diffraction� Shorter incident
wavelengths are diffracted less
� Longer incident wavelengths are diffracted more
� Longer incident wavelengths are diffracted more
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Wave Diffraction� Waves passing through smaller openings are diffracted more
� Waves passing through smaller openings are diffracted more
� Waves passing through larger openings are diffracted less
diffracted morediffracted more
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Wave Diffraction
Short wavelengths
diffract less
around an object
Short wavelengths
diffract less
around an object
Long wavelengths
diffract more
around an object
Long wavelengths
diffract more
around an object
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Summary� Incident/reflected rays are perpendicular to wavefronts� Angle between incident ray & normal = angle of incidence� Angle between reflected ray & normal = angle of reflection� Angle of incidence = angle of reflection� Waves refract when traveling from 1 medium to another� Waves refract when traveling from 1 medium to another� v1/λ1=v2/λ2� Oblique incident rays bend towards normal when entering a
slower medium� As wavelengths become longer they are diffracted more� As an opening becomes larger, waves passing through diffract
less� Particles do not bend around corners, but waves do
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Homework� Reflection, Refraction, and Diffraction
worksheetworksheet