A horizontal glass tube, closed at one end, has a layer of dust laid inside it on its lower side. Sound is emitted from a loudspeaker that is placed near the open end of the tube. The frequency of the sound is varied and, at one frequency, a stationary wave is formed inside the tube so that the dust forms small heaps. The distance between four heaps of dust is $$$30 \mathrm{~cm}$$$. The speed of sound in the tube is $$$330 \mathrm{~m} \mathrm{~s}^{-1}$$$. What is the frequency of the sound emitted by the loudspeaker?

$1650 \mathrm{~Hz}$

$2200 \mathrm{~Hz}$

$3300 \mathrm{~Hz}$

$6600 \mathrm{~Hz}$

Physics

IGCSE&ALevel

CAIE

Exam No：9702_w12_qp_12 Year：2012 Question No：29

Answer:

Knowledge points:

8.1.1 explain and use the principle of superposition in simple applications

8.1.2 show an understanding of experiments that demonstrate stationary waves using microwaves, stretched strings and air columns

8.1.3 explain the formation of a stationary wave using a graphical method, and identify nodes and antinodes

8.2.1 explain the meaning of the term diffraction

8.2.2 show an understanding of experiments that demonstrate diffraction including the diffraction of water waves in a ripple tank with both a wide gap and a narrow gap

8.3.1 understand the terms interference and coherence

8.3.2 show an understanding of experiments that demonstrate two-source interference using water ripples, light and microwaves

8.3.3 understand the conditions required if two-source interference fringes are to be observed

8.3.4 recall and solve problems using the equation m = $\frac{ax}{n}$ for double-slit interference using light

8.4.1 recall and solve problems using the formula d sin i = nm

8.4.2 describe the use of a diffraction grating to determine the wavelength of light (the structure and use of the spectrometer are not included)

Answer:

Knowledge points:

Solution:

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