Physics · Science General

Acoustics and Sound Waves

2,006 Questions

Acoustics and sound waves deal with mechanical vibrations traveling through media like air and water. Key concepts include wave reflection, beats, echoes, the Mach number, and infrasound. These physics fundamentals are regularly tested in general science sections of multiple competitive exams.

Sound wave propagationEchoes and reflectionWave interferenceMach numberInfrasound frequency

Acoustics and Sound Waves Questions

Multiple choice physics stationary waves formation of stationary waves stationary waves and its graphical representation standing waves in strings from moving to stationary stationary (or standing) waves

The frequency of a sound wave is 250 Hz and its wavelength is 100 cm. The distance travelled by a sound wave in the time taken to produce 100 waves is ________.

  1. 100m

  2. 200m

  3. 300m

  4. 400m
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$v = 250 \times 1 = 250  m  s^{-1}$
$t = \displaystyle \frac{100}{250} s = 0.45$
Distance travelled by wave in the time taken to produce 100 waves $=$ v $\times$ time
$= $ 250 $\times$ 0.45
$=112.5m \approx 100m$

Multiple choice physics stationary waves formation of stationary waves stationary waves and its graphical representation standing waves in strings from moving to stationary stationary (or standing) waves

Standing waves are produced in $10m$ long stretched wire. If wire vibrates in five segments and wave velocity is $20m/s$, then the frequency is $(in\ Hz)$

  1. $5$
  2. $10$
  3. $15$
  4. $20$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

For a wire of length L vibrating in n segments, L = n * lambda / 2. Here L = 10m, n = 5, so 10 = 5 * lambda / 2, lambda = 4m. Frequency f = v / lambda = 20 m/s / 4m = 5 Hz.

Multiple choice physics current electricity and magnetism electric bell the magnetic effect of a current electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

Which of the following is a characteristic of a buzzer?

  1. It has different mechanism from electric bell.

  2. It has higher frequency of collision of gong and hammer

  3. It uses only AC power supply

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In a buzzer, the simplest sort of doorbell, an electromagnet is used to operate a self-interrupting circuit. You can see how this system works in the diagram below. Click and hold the doorbell button to see how the buzzer works. ... This breaks the doorbell circuit, which shuts off the electromagnet.characteristic of a buzzer It has higher frequency of collision of gong and hammer

Multiple choice resonance oscillations physics

A resonance tube is resonated with tuning fork of frequency 256 Hz. If the length of first and second resonating air columns are 32 cm and 100 cm, then end correction will be 

  1. $1 cm$
  2. $2 cm$
  3. $4 cm$
  4. $6 cm$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

For a resonance tube, the resonance condition is L + e = (2n-1) * lambda / 4. Using the first two resonances, L1 + e = lambda / 4 and L2 + e = 3 * lambda / 4, we find 2 * (L2 - L1) = lambda. Substituting the values, lambda = 2 * (100 - 32) = 136 cm, so L1 + e = 136 / 4 = 34 cm; thus, e = 34 - 32 = 2 cm.

Multiple choice resonance oscillations physics

Which of the following is an example of acoustic resonance?

  1. Feedback in guitars

  2. A pendulum

  3. Nuclear magnetic resonance

  4. A swing
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$Answer:-$ A

Acoustic resonance is a phenomenon that consists of a given acoustic system amplifying a sound whose frequency matches one of its own natural frequencies of vibration (its resonance frequencies).
The resonance of a tube of air is related to the length of the tube, its shape, and whether it has closed or open ends. Musically useful tube shapes are conical and cylindrical . A pipe that is closed at one end is said to be stopped while an open pipe is open at both ends. Modern orchestral flutes behave as open cylindrical pipes; clarinets and lip-reed instruments (brass instruments) behave as closed cylindrical pipes; and saxophones, bassoons as closed conical pipes. Vibrating air columns also have resonances at harmonics, like strings (in guitars).

Multiple choice resonance oscillations physics

Pushing a person in a swing is a common example of which type of resonance?

  1. Mechanical resonance

  2. Acoustic resonance

  3. Tidal resonance

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

When we push a person in a swing, we generally match the time between two consecutive pushes, with the time, in which swing comes back to its extreme position. In fact we match our pushing frequency with the frequency of swing to get large arc of swing (amplitude), this is a common example of mechanical resonance.

Multiple choice resonance oscillations physics

A cylindrical tube,open at one end and closed at the other,is acoustic unison with an external source of frequency held at the open end of the tube, in its fundamental note. Then:

  1. The displacement wave from the source gets reflected with a phase change of $ \pi $ at the closed end

  2. The pressure wave from the source get reflected without a phase change at the closed end

  3. The wave reflected from the closed end again gets reflected at the open end

  4. The wave reflected from the closed end does not suffer reflection at the open end
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A cylindrical tube,open at one end and closed at the other,is acoustic unison with an external source of frequency held at the open end of the tube, in its fundamental note, then the displacement wave from the source gets reflected with a phase change of  $\pi $ at the closed end.

so the correct option is A.

Multiple choice resonance oscillations physics

For a certain organ pipe open at both ends, the successive resonance frequencies are obtained at $510, 680$ and $850\ Hz$. The velocity of sound in air is $340\ m/s$. The length of the pipe must be:

  1. $2\ m$
  2. $0.5\ m$
  3. $m$
  4. $0.25\ m$
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice resonance oscillations physics

Suggest one way by which rattling sound could be stopped.

  1. Rattling sound can be stopped by changing the speed of the vehicle.

  2. Rattling sound can be stopped by changing the frequency of the vehicle.

  3. Rattling sound can be stopped by changing the vibration of the vehicle.

  4. None of the above.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The cause of rattling sound is resonance and it can be stopped by changing the speed of the vehicle. 

Multiple choice resonance oscillations physics

Some opera singers are able to use their voice to shatter a crystal glass. Which of the phenomenon is used to explain this ? 

  1. Acoustic reflection

  2. Multiple echoes

  3. Interference

  4. Resonance

  5. Beats
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

 When the  external frequency becomes equal to the natural frequency of the body , then the amplitude of vibrations of the body becomes very large , this phenomenon is called resonance .

   When a opera singer  manages his frequency such that it becomes equal to the natural frequency of crystal glass , resonance occurs and glass shatters.

Multiple choice resonance oscillations physics

Your friend is playing a song on a piano. Whenever your friend hits a certain key, the lamp on top of the piano rattles. Explain why the lamp rattles.

  1. The lamp rattles because of the occurring of interference

  2. The lamp rattles because of the occurring of diffraction

  3. The lamp rattles because of the occurring of resonance

  4. None of the above

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

This happens due to resonance (A phenomenon in which a vibrating system or external force drives another system to oscillate with a greater amplitude at a specific frequency). The lamp on top of the piano has a resonant frequency equal to one of the notes being played.

Multiple choice resonance oscillations physics

During resonance, sound waves tend to absorb

  1. more energy

  2. less energy

  3. no energy

  4. infinite energy
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

System to absorb more energy when the frequency of its oscillations matches the system's natural frequency of vibration than it does at other frequencies.

Multiple choice resonance oscillations physics

A glass tube of $1.0 m$ length is filled with water. The water can be drained out slowly at bottom of the tube. If a vibrating turning fork of frequency $500 Hz$ is brought at the upper end of the tube and the velocity of sound is $330 \,\,m\,\,s^{-1}$, then the total number of resonances obtained will be:

  1. 4

  2. 3

  3. 2

  4. 1
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Wavelength of the sound produced is,
$\lambda = \dfrac{Velocity}{Frequency} $


$= \dfrac{330\,\,m\,\,s^{-1}}{500\,\,s^{-1}} = 0.66\,\,m$
The resonance occurs at
$\dfrac{\lambda}{4},\dfrac{3\lambda}{4},\dfrac{5\lambda}{4},\dfrac{7\lambda}{4},.....$
i.e., at $0.165\,\,m, 0.495\,\,m, 0.825\,\,m, 1.155\,\,m$. As the length of the tube is only $1.0\,\,m$, hence $3$ resonance will be observed.

Multiple choice physics study of sound determination of speed of sound by echo problems on sound sound needs a medium

A sound wave travels from west to east, in which direction do the particles of air move?

  1. west-east

  2. south-north

  3. up-down

  4. none of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Sound waves are longitudinal waves and the particles of the air move in direction of propagation sound. So if the wave will travel in west-east direction,the particles of the air also travels in west-east direction.