Interference
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Waves: Interference, Coherence, Path Length, and Power Shift, Slides of Physics
The concepts of interference and coherence in waves, focusing on constructive and destructive interference, path length effects, and power shifts. It covers the principles of superposition, the importance of phase in coherent radiation, and how different path lengths lead to constructive or destructive interference. An example of microwaves reflecting off mirrors illustrates power shifts.
Typology: Slides
2012/2013
1 / 8
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Interference
Overlap
Waves from multiple pointsources overlap.
-^
Crest on crest
-^
Trough on trough
-^
Crest on trough
Overlapping waves adddirectly.
-^
Principle of
superposition
Constructive Interference
When coherent waves havethe same phase the result isconstructive interference.
-^
Amplitudes add
-^
Intensity follows the square ofthe amplitude
m 2
m 2 1
A
A
A
2 1 2 1 2 2 1
(^
I I I I I I
I^
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Destructive Interference
When coherent waves havethe opposite phase the result isdestructive interference.
-^
Cancellation of amplitude
-^
Decreased intensity
1 2
m
m 2 1
A
A
A
2 1 2 1 2 2 1
(^
I I I I I I
I^
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Power Shift
Spacing in coherentelectromagnetic waves resultsin power fluctuations.
Example: microwavesreflecting off mirrors.
-^
Transmitter
T
, monochromatic
waves
-^
Receiver
R
, power depend on
separation
Intensity Pattern
CDs and DVDs are read by intensity difference due tophase shifts.
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