Interference Pt II

  1. Pressure node = _______ antinode and vice versa
    2 cases regarding the two ends of the air columns: 
    (State the cases)
    In case 2, where one end is open and the other closed (a type of displacement function), where is the displacement node vs displacement antinode?
    • displacement antinode 
    • Case 1: Both ends open, e.g. flute
    • Case 2: one end opened and one end close, e.g. pipe organ
    • Displacement Node at closed end
    • Displacement Antinode at open end
  2. In Case 1 (both ends open), both ends are ________ ________. State the formula for the natural frequencies, fn and that of λand what harmonics are to be expected
    • displacement antinodes 
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  3. In Case 2: Pipe open at one end
    The closed end is a ________ _______. The open end is a _______ _______. State the formula for fn and λand state the n series
    • displacement node
    • displacement antinode
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  4. Depict the first, second and third resonance of the following 
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  5. Musicians called f2,f3,...fn overtones
    f2 = ______ harmonic = ______ overtone
    f3 = ______ harmonic = ______ overtone
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    D. All the above
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    • a) f = v/λ1 = v/2L
    • b) f = v/λ1 = v/2L
    • c) f = v/λ1 = v/4L
    • ∴ a=b>c
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    • Lowest frequency is the fundamental frequency f1 = v/2L
    • A is wrong, if we use a thicker string, μ increases and v = (√T/μ) decreases, so f1 decreases
    • **B** is right, increasing tension increases v which is directly proportional to f1
    • C is wrong, plucking the string harder only increases Amplitude
    • D is wrong increasing L would decrease fundamental freq. (v/2L)
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  11. To simplify the mathematical expressions, we take x = 0, Φ10 = Φ20 = π
    State the formulas for:
    D1
    D2
    D (be sure to specify which portion is the lower frequency and which is the higher frequency)
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  12. Temporal interference occurs when the interfering waves have ______ ______ frequencies. 
    Define Beating and Beat frequency (state the formula and explain)
    The human ear can detect a beat frequency up to about ____ beats/second
    • slightly different frequencies 
    • Beating: the periodic variation in amplitude at a given point due to the supersposition of two waves having slightly different frequencies
    • Beat frequency: the number of amplitude maxima one hears per second, it is the difference between the frequencies of the two sources 
    • fbeat = |f1 - f2|
    • 20 beats/second
  13. Restate the beat frequency formula and state the formula for amplitude modulation here (purple arrow): 
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    • fb = |f1 - f2|
    • The amplitude is slowly modulated as 2acos2πfbt
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  14. At the 1st point, the waves are in _____. There is _______ interference. At the 2nd point, the waves are ____ ____ _____. There is _______ interference. At the 3rd point, the waves are _____ _____ _____. There is _______ interference. What would this look like if we had a superposition of the two sound waves
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    • phase
    • constructive interference
    • out of phase
    • destructive interference 
    • back in phase
    • constructive interference 
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  15. This medium oscillates _____ at frequency fosc. The amplitude is ______ ______ at frequency fbeat
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    • rapidly 
    • slowly modulated
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    • fb = |f1-f2|
    • fb = |340 - 341|
    • fb =  1Hz or 1s-1
    • T = 1/fb = 1/1s-1 = 1s
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Author
chikeokjr
ID
345640
Card Set
Interference Pt II
Description
Interference Pt II
Updated