Two coherent narrow slits emitting sound of wavelength
Question: 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 $\Sigma$ at a distance $D(\lambda)$ 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 $O$. Solution:...
Read More →Three sources of sound S1, S2 and S3 of equal intensity are placed
Question: Three sources of sound $S_{1}, S_{2}$ and $S_{3}$ of equal intensity are placed in a straight line with $S_{1} S_{2}=S_{2} S_{3}$. At a point $P_{1}$ far away from the sources, the wave coming from $S_{2}$ is $120^{\circ}$ ahead in phase of that from $S_{1}$. Also, the wave coming from $S_{3}$ is $120^{\circ}$ ahead of that from $S_{2}$. What would be the resultant intensity of sound at $P$ ? Solution:...
Read More →Two speakers S1 and S2, driven by the same amplifier,
Question: Two speakers $S_{1}$ and $S_{2}$, driven by the same amplifier, are placed at $y=1.0 \mathrm{~m}$ and $y=-1.0 \mathrm{~m}$. The speakers vibrate in phase at $600 \mathrm{~Hz}$. A man stands at a point on the $X$-axis at a very large distance from the origin and starts moving parallel to the $Y$ axis. The speed of sound in air is $330 \mathrm{~m} \mathrm{~s}^{-1}$. (a) At what angle $\theta$ will the intensity of sound drop to a minimum for the first time? (b) At what angle will he hear...
Read More →Differentiate each of the following w.r.t.
Question: Differentiate each of the following w.r.t. $x$ : $\tan 3 x$ Solution:...
Read More →The two sources of sound, S1 and S2,
Question: The two sources of sound, $S_{1}$ and $S_{2}$, emitting waves of equal wavelength $20.0 \mathrm{~cm}$, are placed with a separation of $20.0$ cm between them. A detector can be moved on a line parallel to $S_{1} S_{2}$ and at a distance of $20.0 \mathrm{~cm}$ from it. Initially, the detector is equidistant from the two sources. Assuming that the waves emitted by the sources are in detector should be shifted to detect a minimum of sound. Solution:...
Read More →Two stereo speakers are separated by
Question: Two stereo speakers are separated by a distance of $2.40 \mathrm{~m}$. A person stands at a distance of $3.20 \mathrm{~m}$ directly in front of one of the speakers as shown in figure. Find the frequencies in the audible range $(20-2000 \mathrm{~Hz})$ for which the listener will hear a minimum sound intensity. Speed of sound in air $=320 \mathrm{~m} \mathrm{~s}^{-1}$. Solution:...
Read More →A source S and a detector D are placed at a distance d apart.
Question: A source $S$ and a detector $D$ are placed at a distance $d$ apart. A big cardboard is placed at a distance $\sqrt{2} d$ from the source and the detector as shown in figure. The source emits a wave of wavelength $=d / 2$ 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 direc...
Read More →Differentiate each of the following w.r.t
Question: Differentiate each of the following w.r.t. $\mathrm{x}$ : $\cos 5 x$ Solution:...
Read More →A source of sound S and detector D are placed
Question: A source of sound $S$ and detector $D$ are placed at some distance from one another. a big cardboard is placed near the detector and perpendicular to the line $S D$ as shown in figure. It is gradually moved away and it is found that the intensity changes from a maximum to a minimum as the board is moved through a distance of $20 \mathrm{~cm}$. Find the frequency of the sound emitted. Velocity of sound in air is $336 \mathrm{~m} \mathrm{~s}^{-1}$. Solution:...
Read More →Differentiate each of the following w.r.t. x
Question: Differentiate each of the following w.r.t. $x$ : $\sin 4 x$ Solution:...
Read More →Two audio speakers are kept some distance apart
Question: Two audio speakers are kept some distance apart and are driven by the same amplifier system. A person is sitting at a place $6.0 \mathrm{~m}$ from one of the speakers and $6.4 \mathrm{~m}$ from the other. If the sound signal is continuously varied from $500 \mathrm{~Hz}$ to $5000 \mathrm{~Hz}$, what are the frequencies for which there is a destructive interference at the place of the listener? Speed of sound in air $=320$ $\mathrm{m} \mathrm{s}^{-1}$. Solution:...
Read More →In Quincke's experiment, the sound intensity has a minimum value
Question: In Quincke's experiment, the sound intensity has a minimum value / at a particular position. As the sliding tube is pulled out by a distance of $16.5 \mathrm{~mm}$, the intensity increases to a maximum of $9 /$. Take the speed of sound in air to be $330 \mathrm{~m} \mathrm{~s}^{-1}$. (a) Find the frequency of the sound source. (b) Find the ratio of the amplitudes of the two waves arriving at the detector assuming that it does not change much between the positions of minimum intensity a...
Read More →In Quincke's experiment the sound detected is changed
Question: In Quincke's experiment the sound detected is changed from a maximum to a minimum when the sliding tube is moved through a distance of $2.50 \mathrm{~cm}$. Find the frequency of sound if the speed of sound in air is $340 \mathrm{~m} \mathrm{~s}^{-1}$. Solution:...
Read More →The noise level in a classroom in absence of the teacher
Question: The noise level in a classroom in absence of the teacher is $50 \mathrm{~dB}$ when 50 students are present. Assuming that on the average each student output same sound energy per second, what will be the noise level if the number of students is increased to 100 ? Solution:...
Read More →If the sound level in a room is increased from
Question: If the sound level in a room is increased from $50 \mathrm{~dB}$ to $60 \mathrm{~dB}$, by what factor is the pressure amplitude increased? Solution:...
Read More →Sound with intensity larger than 120 dB appears pain full to a person.
Question: Sound with intensity larger than $120 \mathrm{~dB}$ appears pain full to a person. A small speaker delivers $2.0$ W of audio output. How close can the person get to the speaker without hurting his ears? Solution:...
Read More →If the intensity of sound is doubled,
Question: If the intensity of sound is doubled, by how many decibels does the sound level increase? Solution:...
Read More →The sound level at a point 5.0 m away from a point source is 40 dB.
Question: The sound level at a point $5.0 \mathrm{~m}$ away from a point source is $40 \mathrm{~dB}$. What will be the level at a point $50 \mathrm{~m}$ away from the source? Solution:...
Read More →The intensity of sound from a point source is
Question: The intensity of sound from a point source is $1.0 \times 10^{-8} \mathrm{~W} \mathrm{~m} \mathrm{~m}^{-2}$ at a distance of $5.0 \mathrm{~m}$ from the source. What will be the intensity at a distance of $25 \mathrm{~m}$ from the source? Solution:...
Read More →A sources of sound operates at
Question: A sources of sound operates at $2.0 \mathrm{kHz}, 20 \mathrm{~W}$ emitting sound uniformly in all directions. The speed of sound in air is $340 \mathrm{~m}$ $\mathrm{s}^{-1}$ and the density of air is $1.2 \mathrm{~kg} \mathrm{~m}^{-3}$. (a) What is the intensity at a distance of $6.0 \mathrm{~m}$ from the source? (b) What will be the pressure amplitude at this point? (c) What will be the displacement amplitude at this point? Solution:...
Read More →Calculate the bulk modulus of air from the following data
Question: Calculate the bulk modulus of air from the following data about a sound wave of wavelength $35 \mathrm{~cm}$ travelling in air. The pressure at a point varies between $\left(1.0 \times 10^{5} \pm 14\right) \mathrm{Pa}$ and the particles of the air vibrate in simple harmonic motion of amplitude $5.5 \times 10^{-6} \mathrm{~m}$. Solution:...
Read More →Find the change in the volume of
Question: Find the change in the volume of $1.0$ litre kerosene when it is subjected to an extra pressure of $2.0 \times 10^{5} \mathrm{~N} \mathrm{~m}^{-2}$ from the following data. Density of kerosene $=800 \mathrm{~kg} \mathrm{~m}^{-3}$ and speed of sound in kerosene $=1330 \mathrm{~ms}^{-1}$. Solution:...
Read More →The absolute temperature of air in a region linearly increases
Question: The absolute temperature of air in a region linearly increases from $T_{1}$ to $T_{2}$ in a space of width d. Find the time taken by a sound wave to go through the region in terms of $T_{1}, T_{2}, d$ and the speed $v$ of sound at $273 \mathrm{~K}$. Evaluate this time for $T_{1}=280$ $\mathrm{K}, T_{2}=310 \mathrm{~K}, d=33 \mathrm{~m}$ and $v=330 \mathrm{~m} \mathrm{~s}^{-1}$. Solution:...
Read More →At what temperature will the speed of sound
Question: At what temperature will the speed of sound be double of its value at $0^{\circ} \mathrm{C}$ ? Solution:...
Read More →The speed of sound as measured by a student
Question: The speed of sound as measured by a student in the laboratory on a winter day is $340 \mathrm{~m} \mathrm{~s}$ when the room temperature is ${\mathrm{C} 17^{\circ}}^{\circ}$. What speed will be measured by another student repeating the experiment on a day when the room temperature is $32^{\circ} \mathrm{C}$ ? Solution:...
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