Waves

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Waves

Celtic Harp

Irish folk tunes

arranged by

Howard Baer


Propagation of

Waves

Key Terms

★Reflection

★Refraction

★Absorption


Diffraction

Diffraction is

significant only when

D ≤ λ


Interference

★Interference occurs

whenever two waves

occupy the same space

at the same time.


Resultant Wave

★The combined wave

formed by the superposition

of two individual

waves


Constructive Interference

★The two interfering waves

reinforce one another

★Occurs when the two waves

are in phase


Constructive Interference


Destructive Interference


Destructive Interference

★The two interfering waves

cancel one another

★Occurs when the two waves

are out of phase


Video I-3

Interference: Transverse

Waves on a String.


Constructive Interference –

Waves

2

1.5

1

0.5

0

-0.5

-1

-1.5

-2


Destructive Interference –

Waves

1

0.5

0

-0.5

-1


Constructive Interference

(unequal amplitudes)

2

1.5

1

0.5

0

-0.5

-1

-1.5

-2


Destructive Interference

(unequal amplitudes)

1

0.5

0

-0.5

-1


Sound From Two Sources


Sound From Two Sources

★Constructive interference

occurs when

L 1 - L 2 = n λ


Sound From Two Sources

★Destructive interference

occurs when

L 1 - L 2 = (n+ ½)λ


Video II-5

Interference of Sound Waves


Beats

★Occur when two waves of

slightly different

frequency interfere


Beats

1

0.5

0

-0.5

-1

2.5

2

1.5

1

0.5

0

-0.5

-1

-1.5

-2


Video II-6

Beats


Beat Frequency

f beat = |f 1 -f 2 |

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