Pressure Wave vs Displacement Wave

Q. The phase difference between the displacement wave and the pressure wave in sound wave is

1. $\frac{\pi }{2}$
2. $\frac{\pi }{4}$
3. $\frac{\pi }{6}$
4. $\frac{\pi }{3}$

Q. If pressure amplitude of a sound wave in a medium is tripled and the wavelength is doubled then amplitude of displacement of the particles in the medium becomes $x$ times of initial value. The value of $x$ is

1. $5$
2. $3$
3. $2$
4. $6$

Q. A sound wave of wavelength $40\text{cm}$ travels in air. If the difference between maximum and minimum pressures at a given point is $1.0\times {10}^{-3}{\text{N/m}}^2$, then find the amplitude of vibrations of the particles of the medium.
[Bulk modulus of air is $1.4\times {10}^5{\text{N/m}}^2$]

1. $3.3\times {10}^{-10}\text{m}$
2. $2.3\times {10}^{-10}\text{m}$
3. $4.3\times {10}^{-10}\text{m}$
4. $5.3\times {10}^{-10}\text{m}$

Q. Maximum sound pressure tolerable by the human ear is $30{\text{N/m}}^2$. For sound of frequency ${10}^3\text{Hz}$ and speed $300\text{m/s}$, the maximum displacement of particles of medium is
[density of air $1.5{\text{kg/m}}^3)$]

1. $\frac{1}{6\pi }\times {10}^{-4}\text{m}$
2. $\frac{1}{5\pi }\times {10}^{-4}\text{m}$
3. $\frac{1}{3\pi }\times {10}^{-4}\text{m}$
4. $\frac{1}{4\pi }\times {10}^{-4}\text{m}$

Q. What is the displacement amplitude of a sound wave having frequency $100\text{Hz}$ and pressure amplitude $10\text{Pa}$?
[speed of sound in air $=340\text{m/s}$ and density of air $=1.29{\text{kg/m}}^3$]

1. $3.6\times {10}^{-5}\text{m}$
2. $4.5\times {10}^{-5}\text{m}$
3. $2.5\times {10}^{-5}\text{m}$
4. $1.5\times {10}^{-5}\text{m}$

Q.

The pressure variation equation of a sound wave propagating in a medium with pressure amplitude $P_0$ is

$P=P_{0}sin\omega (t-\frac{x}{v})$

Inference:

In the tube where this wave is propagating if we measure pressure, then the maximum pressure measured will be _{$P_0$} atm and Minimum pressure measured will be _{$-P_0$} atm as maximum $\&$ minimum values of sin $\theta$ is (+1/-1).

1. Both Statement and Inference are wrong

2. Both Statement and Inference are correct

3. Statement is correct, Inference is wrong

4. Statement is wrong, Inference is correct

Q.

Explain why (or how):
a) In a sound wave, a displacement node is a pressure antinode and vice versa,
b) Bats can ascertain distances, directions, nature, and sizes of the obstacles without any “eyes”,
c) A violin note and sitar note may have the same frequency, yet we can distinguish between the two notes,
d) Solids can support both longitudinal and transverse waves, but only longitudinal waves can propagate in gases, and
e) The shape of a pulse gets distorted during propagation in a dispersive medium.

Q. The variation in pressure in the medium due to propagation of sound is represented as

Which of the following graph correctly represent the displacement of particles of the medium?

1. 
2. 
3. 
4. 

Q. For a sound wave travelling towards +x direction, sinusoidal longitudinal displacement $\xi$ at a certain time is given as a function of x(Figure). If bulk modulus of air is $B=5\times {10}^{5}N/m^2$, the variation of pressure excess will be

1. 
2. 
3. 
4. 

Q. If the pressure variation in the medium is represented by equation $P=\Delta P_o\sin (kx-\omega t)$ then the resulting density variation in medium is suitably represented by equation

1. $\rho =\Delta {\rho }_o\cos (kx-\omega t)$
2. $\rho =-\Delta {\rho }_o\cos (kx-\omega t)$
3. $\rho =\Delta {\rho }_o\sin (kx-\omega t)$
4. $\rho =-\Delta {\rho }_o\sin (kx-\omega t)$

Q. Consider the following statements about sound passing through a gas.
(A) The pressure of the gas at a point oscillates in time.
(B) The position of a small layer of the gas oscillates in time.

1. B is correct but A is wrong.
2. Both A and B are wrong.
3. Both A and B are correct.
4. A is correct but B is wrong.

Q. Sound is a form of energy. True or false.

1. true
2. false

Q. What adjustments would you make for tuning a stringed instrument for it to emit a note of a desired frequency ?

Q.

Calculate the bulk modulus of the air from the following data about a sound wave of wavelength $35cm$ travelling in air. the pressure at a point varies between $\left(1.0\times {10}^5\pm 14\right)Pa$ and the particles of the air vibrate in simple harmonic motion of amplitudes $5.5\times {10}^{-6}m$.

1. $3.2\times {10}^{2}N{m}^2$

2. $5.5\times {10}^{6}N{m}^2$

3. $1.4\times {10}^{5}N{m}^2$

4. None of these

Q. The difference between the apparent frequency of a source of sound as perceived by the observer during its approach and recession is $2\%$ of the frequency of the source. If the speed of the sound in air is $300ms$, the velocity of the source is :

1. $1.5ms$
2. $12ms$
3. $6ms$
4. $3ms$

Q. The phase difference between the displacement wave and the pressure wave in sound wave is

1. $\frac{\pi }{3}$
2. $\frac{\pi }{2}$
3. $\frac{\pi }{4}$
4. $\frac{\pi }{6}$

Q. The variation of pressure in a medium due to propagation of sound is represented as

Which of the following graph correctly represents the displacement of particles of the medium?

1. 
2. 
3. 
4. 

Q. Why are musical instruments like the guitar provided with a hollow box?

Q. When interference is produced by two progressive waves of equal frequencies, then the maximum intensity of the resulting sound are N times the intensity of each of the component waves. The value of N is

1. 4
2. 8
3. 2
4. 1

Q. Make a list of five musical instruments. State how each of them produce sound.

Musical instrument	The way it produces sound

Q. There are three sources of sound of equal intensity with frequencies 400, 401, 402 vibrations/sec. The number of beats heard per second is

1. 1
2. 2
3. 3
4. 0

Q. Name musical instruments which produce sound by vibrating strings?

1. Bass
2. Viola
3. Cello
4. All of the above

Q. Three sound waves of equal amplitudes have frequencies $(v-1),v,(v+1)$. They superpose to give beats. The number of beats produced per second will be

1. $4$
2. $3$
3. $2$
4. $1$

Q. Two waves of same amplitude superimpose to produce two beats per second. What is the ratio of maximum loudness to that of one of the waves?

1. $2$
2. $4$
3. $8$
4. $\infty$

Q. Which of the following is not correct regarding the experiment to determine the velocity of sound in laboratory by resonance tube method?

1. the vibrating tuning fork should be held horizontally over the open end of the tube
2. the resonance tube apparatus should be kept inclined
3. the prongs of vibrating tuning fork should not touch the tube
4. the turning fork should be struck gently against a soft rubber pad

Q. Name two percussion instruments

Q. Two sound waves of frequencies of 400 Hz and 300 Hz have an amplitude in the ratio 1 : 2. Then, the intensities of these waves will be in the ratio

1. 4 : 3
2. 1 : 4
3. 16 : 9
4. 4 : 9

Q. In case of sound, we can study the disturbance due to pressure wave and displacement wave. What is the phase difference between these two?

1. 0
2. $\pi$
3. $\frac{\pi }{6}$
4. $\frac{\pi }{2}$

Q. The instruments that produce sound by vibrating strings are called string instruments.

1. True
2. False

Q. Two sound waves travelling in the same direction are represented by equations $Y_1=A_{1}Sin504\pi t$; $Y_2=A_{2}Sin512\pi t$. These two sound waves superpose to produce beats. The intensity of sound changes from minimum to maximum in a time of

1. 1/2 s
2. 1/4s
3. 1/8 s
4. 1/16 s