Question types

Sound Waves question types

115 questions across 6 question groups — pick any mix to generate a Physics paper with step-by-step answer keys.

115
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6
Question groups
5
Question types
Sample Questions

Sound Waves questions

One sample from each question group in this chapter. Select any group above to see the full set with answer keys.

Consider the following statements about sound passing through a gas.
  1. The pressure of the gas at a point oscillates in time.
  2. The position of a small layer of the gas oscillates in time.
  • Both A and B are correct.
     
  • B
    A is correct but B is wrong.
     
  • C
    B is correct but A is wrong.
     
  • D
    Both A and B are wrong.

Answer: A.

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A tuning fork of frequency 512Hz is vibrated with a sonometer wire and 6 beats per second are heard. The beat frequency reduces if the tension in the string is slightly increased. The original frequency of vibration of the string is:
  • 506Hz
  • B
    512Hz
  • C
    518Hz
  • D
    524Hz.

Answer: A.

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A small source of sound moves on a circle as shown$-$in figure and an observer is sitting at $0$. Let $v_1, v_2, v_3$ be the frequencies heard when the source is at $A, B$ and $C$ respectively.
  • A
    $v_1 > v_2 > v_3$
  • B
    $v_1=v_2 > v_3$
  • $v_2 > v_3 > v_1$
  • D
    $v_1 > v_2 > v_2$.

Answer: C.

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The speed of sound in a medium depends on:
  • A
    The elastic property but not on the inertia property.
  • B
    The inertia property but not on the elastic property.
  • The elastic property as well as the inertia property.
  • D
    Neither the elastic property nor the inertia property.

Answer: C.

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Two sound waves move in the same direction in the same medium. The pressure amplitudes of the waves are equal but the wavelength of the first wave is double the second. Let the average power transmitted across a cross $-$ section by the first wave be $P_1$ and that by the $1$ second wave be $P_2$. Then,
  • $P_1=P_2$
  • B
    $P_1=4 P_2$
  • C
    $P_2=2 P_1$
  • D
    $\mathrm{P}_2=4 \mathrm{P}_1$

Answer: A.

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A Kundt's tube apparatus has a copper rod of length 1.0m clamped at 25cm from one of the ends. The tube contains air in which the speed of sound is 340m/s. The powder collects in heaps separated by a distance of 5.0cm. Find the speed of sound waves in copper.
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The fundamental frequency of a closed pipe is 293Hz when the air in it is at a temperature of $20^\circ C$. What will be its fundamental frequency when the temperature changes to $22^\circ C?$
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Figure, shows two coherent sources $S_1$ and $S_2$ which emit sound of wavelength $\lambda$ in phase. The separation between the sources is $3\lambda.$ A circular wire of large radius is placed in such a way that $S_1S_2$ lies in its plane and the middle point of $S_1S_2$ is at the centre of the wire. Find the angular positions $\theta$ on the wire for which constructive interference takes place.
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Sound with intensity larger than 120dB appears painful to a person. A small speaker delivers 2.0W of audio output. How close can the person get to the speaker without hurting his ears?
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Find the minimum and maximum wavelengths of sound in water that is in the audible range (20-20000Hz) for an average human ear. Speed of sound in water = 1450m/s.
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Q 133 Marks Question3 Marks
A source emitting a sound of frequency v is placed at a large distance from an observer. The source starts moving towards the observer with a uniform acceleration a. Find the frequency heard by the observer corresponding to the wave emitted just after the source starts. The speed of sound in the medium is u.
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Q 143 Marks Question3 Marks
A train approaching a platform at a speed of 54km/h sounds a whistle. An observer on the platform finds its frequency to be 1620Hz. The train passes the platform keeping the whistle on and without slowing down. What frequency will the observer hear after the train has crossed the platfrom? The speed of sound in air = 332m/s.
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Q 153 Marks Question3 Marks
A copper rod of length 1.0m is clamped at its middle point. Find the frequencies between 20Hz - 20,000Hz at which standing longitudinal waves can be set up in the rod. The speed of sound in copper is 3.8km/s.
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Q 163 Marks Question3 Marks
The equation of a travelling sound wave is $\text{y}=6.0\sin(600\text{t}-1.8\text{x})$ where y is measured in $10^{-5}m$, t in second and x in metre.
  1. Find the ratio of the displacement amplitude of the particles to the wavelength of the wave.
  2. Find the ratio of the velocity amplitude of the particles to the wave speed.
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Q 173 Marks Question3 Marks
Two coherent narrow slits emitting sound of wavelength $\lambda$ in the same phase are placed parallel to each other at a small separation of $2\lambda.$ The sound is detected by moving a detector on the screen $\sum$ at a distance $\text{D}(>>\lambda)$ from the slit $S_1$ as shown in figure. Find the distance x such that the intensity at P is equal to the intensity at 0.
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A boy riding on his bike is going towards east at a speed. of $4\sqrt{2}\text{m/s}$ At a certain point he produces a sound pulse of frequency 1650Hz that travels in air at a speed of 334m/s. A second boy stands on the ground 45° south of east from him. Find the frequency of the pulse as received by the second boy.
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A piston is fitted in a cylindrical tube of small cross-section with the other end of the tube open. The tube resonates with a tuning fork of frequency 512Hz. The piston is gradually pulled out of the tube and it is found that a second resonance occurs when the piston is pulled out through a distance of 32.0cm. Calculate the speed of sound in the air of the tube.
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A source S and a detector D are placed at a distance d apart. A big cardboard is placed at a distance $\sqrt{2}\text{d}$ from the source and the detector as shown in figure, The source emits a wave of wavelength $=\frac{\text{d}}{2}$ which is received by the detector after reflection from the cardboard. It is found to be in phase with the direct wave received from the source. By what minimum distance should the cardboard be shifted away so that the reflected wave becomes out of phase with the direct wave?
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An operator sitting in his base camp sends a sound signal of frequency 400Hz. The signal is reflected back from a car moving towards him. The frequency of the reflected sound is found to be 410Hz. Find the speed of the car. Speed of sound in air = 324m/s.
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A tuning fork of unknown frequency makes 5 beats per second with another tuning fork which can cause a closed organ pipe of length 40cm to vibrate in its fundamental mode. The beat frequency decreases when the first tuning fork is slightly loaded with wax. Find its original frequency. The speed of sound in air is 320m/s.
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Two submarines are approaching each other in a calm sea. The first submarine travels at a speed of 36km/h and the other at 54km/h relative to the water. The first submarine sends a sound signal (sound waves in water are also called sonar) at a frequency of 2000Hz.
  1. At what frequency is this signal received by the second submarine?
  2. The signal is reflected from the second submarine. At what frequency is this signal received by the first submarine. Take the speed of the sound wave in water to be 1500m/s.
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At a prayer meeting, the disciples sing JAI-RAM JAI-RAM. The sound amplified by a loudspeaker comes back after reflection from a building at a distance of 80m from the meeting. What maximum time interval can be kept between one JAI-RAM and the next JAI-RAM so that the echo does not disturb a listener sitting in the meeting. Speed of sound in air is 320m/s.
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Find the change in the volume of 1.0 litre kerosene when it is subjected to an extra pressure of $2.0 x 10^5N/m^2$ from the following data. Density of kerosene $= 800kg/m^3$ and speed of sound in kerosene $= 1330m/s.$
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Two stereo speakers are separated by a distance of 2.40m. A person stands at a distance of 3.20m directly in front of one of the speakers as shown in figure, Find the frequencies in the audible range (20-2000Hz) for which the listener will hear a minimum sound intensity. Speed of sound in air = 320m/s.
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