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A pipe closed at one end can produce overtones at frequencies 640 Hz, 896 Hz, and 1152 Hz. Calculate the fundamental frequency. - Physics

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प्रश्न

A pipe closed at one end can produce overtones at frequencies 640 Hz, 896 Hz, and 1152 Hz. Calculate the fundamental frequency.

संख्यात्मक

उत्तर १

The difference between the given overtone frequencies is 256 Hz. This implies that they are overtones that follow one another. Let nc represent the fundamental frequency of the closed pipe and nq, nq-1 represent the frequencies of the qth, (q + 1)th and (q + 2)th consecutive overtones, where q is an integer.

Data: nq = 640 Hz, nq-1 = 896 Hz, nq+2 = 1152 Hz Since only odd harmonics exist as overtones,,

nq = (2q + 1) nc

and nq+1 = [2(q + 1) + 1] nc = (2q + 3) nc

∴ `("n"_("q+1")/("n"_"q"))=(2"q" +3)/(2"q"+1)=896/640=7/5`

∴  `(2"q" + 3)/(2"q"+1)=7/5`

∴  7(2q + 1) = 5(2q + 3)

∴ 14q + 7 = 10q + 15

∴ 4q = 8

∴ q = 2

As a result, the second, third, and fourth overtones, i.e. the fifth, seventh, and ninth harmonics, correspond to the three stated frequencies.

∴ 5nc = 640 ∴ bc = 128 Hz

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उत्तर २

Given: Let frequency for pth overtones

∴ (2p - 1)n = 640         ...(1)

(2p + 1)n = 896           ...(2)

(2p + 3)n = 1152         ...(3)

To find: n = ?

Subtracting (1) from (2)

(2p + 1)n - (2p - 1)n = 896 - 640

2p.n + n - 2pn + n = 256

2n = 128 Hz

Also, subtracting equation (2) from equation (3)

(2p + 3)n - (2p + 1)n = 1152 - 896

n(2p + 3 - 2p - 1) = 256

∴ 2n = 256

∴ n = 128 Hz

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Harmonics and Overtones
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अध्याय 6: Superposition of Waves - Exercises [पृष्ठ १५७]

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बालभारती Physics [English] 12 Standard HSC Maharashtra State Board
अध्याय 6 Superposition of Waves
Exercises | Q 15 | पृष्ठ १५७

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