JEE Questions for Physics Waves Quiz 15 - MCQExams.com

A metal wire of linear mass density of 9.8 g/m is stretched with a tension of 10 kg weight between two rigid supports 1 metre apart. The wire passes at its middle point between the poles of a permanent magnet, and it vibrates in resonance when carrying an alternating current of frequency n. The frequency n of the alternating source is
  • 25 Hz
  • 50 Hz
  • 100 Hz
  • 200 Hz
A wire of density 9 × 103 kg/m3 is stretched between two clamps 1 m apart and is subjected to an extension of 4.9 ×10–4m. The lowest frequency of transverse vibration in the wire is (Y = 9 × 1010 N/m2)
  • 40 Hz
  • 35 Hz
  • 30 Hz
  • 25 Hz
An open pipe is in resonance in its 2nd harmonic with tuning fork of frequency f1. Now it is closed at one end. If the frequency of the tuning fork is increased slowly from f1 then again a resonance is obtained with a frequency f2.If in this case the pipe vibrates nth harmonics then

  • Physics-Waves-96851.png
  • 2)
    Physics-Waves-96852.png

  • Physics-Waves-96853.png

  • Physics-Waves-96854.png
Two speakers connected to the same source of fixed frequency are placed 2.0 m apart in a box. A sensitive microphone placed at a distance of 4.0 m from their midpoint along the perpendicular bisector shows maximum response. The box is slowly rotated until the speakers are in line with the microphone. The distance between the midpoint of the speakers and the microphone remains unchanged. Exactly five maximum responses are observed in the microphone in doing this. The wavelength of the sound wave is
  • 0.6 m
  • 0.2 m
  • 0.4 m
  • 0.8 m
A wire of 9.8 × 10–3kg m–1 passes over a frictionless light pulley fixed on the top of a frictionless inclined plane which makes an angle of 30° with the horizontal. Masses m and M are tied at the two ends of wire such that m rests on the plane and M hangs freely vertically downwards. The entire system is in equilibrium and a transverse wave propagates along the wire with a velocity of 100 ms–1. Choose the correct option
Physics-Waves-96857.png
  • m = 20 kg
  • m = 5 kg
  • m = 2 kg
  • m = 7 kg
A man standing in front of a mountain beats a drum at regular intervals. The rate of drumming is generally increased and he finds that the echo is not heard distinctly when the rate becomes 40 per minute. He then moves nearer to the mountain by 90 m and finds that echo is again not heard when the drumming rate becomes 60 per minute. The distance between the mountain and the initial position of the man is
  • 205 m
  • 300 m
  • 180 m
  • 270 m
Two loudspeakers L1 and L2 driven by a common oscillator and amplifier, are arranged as shown. The frequency of the oscillator is gradually increased from zero and the detector at D records a series of maxima and minima. If the speed of sound is 330 ms–1 then the frequency at which the first maximum is observed is
Physics-Waves-96860.png
  • 165 Hz
  • 330 Hz
  • 496 Hz
  • 660 Hz
A vibrating string of certain length 1 under a tension T resonates with a mode corresponding to the first overtone (third harmonic) of an air column of length 75 cm inside a tube dosed at one end. The string also generates 4 beats per second when excited along with a tuning fork of frequency n. Now when the tension of the string is slightly increased the number of beats reduces to 2 per second. Assuming the velocity of sound in air to be 340 m/s, the frequency n of the tuning fork in Hz is
  • 344
  • 336
  • 117.3
  • 109.3
Vibrating tuning fork of frequency n is placed near the open end of a long cylindrical tube. The tube has a side opening and is fitted with a movable reflecting piston. As the piston is moved through 8.75 cm, the intensity of sound changes from a maximum to minimum. If the speed of sound is 350 m/s. Then n is
Physics-Waves-96863.png
  • 500 Hz
  • 1000 Hz
  • 2000 Hz
  • 4000 Hz
A stone is hung in air from a wire which is stretched over a sonometer. The bridges of the sonometer are L cm apart when the wire is in unison with a tuning fork of frequency N. When the stone is completely immersed in water, the length between the bridges is l cm for re-establishing unison, the specific gravity of the material of the stone is

  • Physics-Waves-96865.png
  • 2)
    Physics-Waves-96866.png

  • Physics-Waves-96867.png

  • Physics-Waves-96868.png
Three waves of equal frequency having amplitudes 10µm, 4µm and 7µm arrive at a given point with successive phase difference of π/2. The amplitude of the resulting wave in µm is given by
  • 7
  • 6
  • 5
  • 4
There are three sources of sound of equal intensity with frequencies 400, 401 and 402 v/sec. The number of beats heard per second is
  • 0
  • 1
  • 2
  • 3
A tuning fork of frequency 340 Hz is vibrated just above the tube of 120 cm height. Water is poured slowly in the tube. What is the minimum height of water necessary for the resonance (speed of sound in the air = 340 m/sec)
  • 15 cm
  • 25 cm
  • 30 cm
  • 45 cm
In Melde\'s experiment, the string vibrates in 4 loops when a 50 gram weight is placed in the pan of weight 15 gram . To make the string to vibrates in 6 loops the weight that has to be removed from the pan is
  • 0.0007 kg wt
  • 0.0021 kg wt
  • 0.036 kg wt
  • 0.0029 kg wt
A massless rod is suspended by two identical strings AB and CD of equal length. A block of mass m is suspended from point O such that BO is equal to \'x\'. Further, it is observed that the frequency of 1st harmonic (fundamental frequency) in AB is equal to 2nd harmonic frequency in CD. Then, length of BO is
Physics-Waves-96874.png

  • Physics-Waves-96875.png
  • 2)
    Physics-Waves-96876.png

  • Physics-Waves-96877.png

  • Physics-Waves-96878.png
Two waves y1 = A cos (0.5 πx – 100πt) and y2 = A cos (0.46 πx – 92πt ) are travelling in a pipe placed along x-axis. Find the number of times intensity is maximum in time interval of 1 sec.
  • 4
  • 6
  • 8
  • 10
A student is performing the experiment of Resonance Column. The diameter of the column tube is 4 cm. The frequency of the tuning fork is 512 Hz. The air temperature is 38°C in which the speed of sound is 336 m/s. The zero of the meter scale coincides with the top end of the Resonance column tube. When the first resonance occurs, the reading of the water level in the column is
  • 14.0 cm
  • 15.2 cm
  • 16.4 cm
  • 17.6 cm

Physics-Waves-96882.png
  • I, II and III
  • II only
  • I and III
  • III only
Two pulses in a stretched string whose centres are initially 8 cm apart are moving towards each other as shown in the figure. The speed of each pulse is 2 cm/s. After 2 seconds, the total energy of the pulses will be
Physics-Waves-96884.png
  • Zero
  • Purely kinetic
  • Purely potential
  • Partly kinetic and partly potential
The figure shows four progressive waves A, B, C, and D with their phases expressed with respect to the wave A. It can be concluded from the figure that
Physics-Waves-96885.png
  • The wave C is ahead by a phase angle of π/ 2 and the wave B lags behind by a phase angle of π /2
  • The wave C lags behind by a phase angle of π /2 and the wave B is ahead by a phase angle of π /2
  • The wave C is ahead by a phase angle of π and the wave B lags behind by a phase angle of π
  • The wave C lags behind by a phase angle of π0020and the wave B ahead by a phase angle of π
The diagram below shows the propagation of a wave. Which points are in same phase?
Physics-Waves-96887.png
  • F, G
  • C and E
  • B and G
  • B and F

Physics-Waves-96889.png
  • (a)
  • (b)
  • (c)
  • (d)
Figure here shows an incident pulse P reflected from a rigid support. Which one of A, B, C, D represents the reflected pulse correctly?
Physics-Waves-96891.png

  • Physics-Waves-96892.png
  • 2)
    Physics-Waves-96893.png

  • Physics-Waves-96894.png

  • Physics-Waves-96895.png
Which of the following curves represents correctly the oscillation given by y = y0 sin (ωt – ɸ), where 0 < ɸ < 90?
Physics-Waves-96896.png
  • A
  • B
  • C
  • D
The correct graph between the frequency n and square root of density (ρ) of a wire, keeping its length, radius and tension constant, is

  • Physics-Waves-96898.png
  • 2)
    Physics-Waves-96899.png

  • Physics-Waves-96900.png

  • Physics-Waves-96901.png
A sound source emits sound waves in a uniform medium. If energy density is E and maximum speed of the particles of the medium is vmax .The plot between E and vmax is best represented by

  • Physics-Waves-96903.png
  • 2)
    Physics-Waves-96904.png

  • Physics-Waves-96905.png

  • Physics-Waves-96906.png
If the speed of the wave shown in the figure is 330m/s in the given medium, then the equation of the wave propagating in the positive x-direction will be (all quantities are in M.K.S. units)
Physics-Waves-96908.png
  • y = 0.05 sin 2π (4000 t – 12.5x)
  • y = 0.5 sin 2π (4000 t – 122.5 x)
  • y = 0.05 sin 2π (3300 t – 10 x)
  • y = 0.05 sin 2π (3300 x – 10 t)
Two pulses travel in mutually opposite directions in a string with a speed of 2.5 cm/s as shown in the figure. Initially the pulses are 10 cm apart. What will be the state of the string after two seconds?

  • Physics-Waves-96910.png
  • 2)
    Physics-Waves-96911.png

  • Physics-Waves-96912.png

  • Physics-Waves-96913.png
Two tuning forks P and Q are vibrated together. The number of beats produced are represented by the straight line OA in the following graph. After loading Q with wax again these are vibrated together and the beats produced are represented by the line OB. If the frequency of P is 341Hz, the frequency of Q will be
Physics-Waves-96915.png
  • 341 Hz
  • 338 Hz
  • 344 Hz
  • None of these
An observer starts moving with uniform acceleration a toward a stationary sound source emitting a whistle of frequency n. As the observer approaches source, the apparent frequency, heard by the observer varies with time

  • Physics-Waves-96917.png
  • 2)
    Physics-Waves-96918.png

  • Physics-Waves-96919.png

  • Physics-Waves-96920.png
A wave is travelling along a string. At an instant, shape of the string is as shown in fig. At this instant, point A is moving upwards. Which of the following statements is/are correct?
Physics-Waves-96922.png
  • The wave is travelling to the right
  • Displacement amplitude of the wave is equal to displacement of B at this instant
  • At this instant velocity of C is also directed upwards
  • Phase difference between A and C may be equal to π/2
The displacement-time graphs for two sound waves A and B are shown in the figure, then the ratio of their intensities IA/ IB is equal to
Physics-Waves-96924.png
  • 1 : 4
  • 1 : 16
  • 1 : 2
  • 1 : 1
A wave motion has the function y = a0 sin (ωt – kx). The graph in figure shows how the displacement y at a fixed point varies with time t. Which one of the labelled points shows a displacement equal to that at the position x = π/2k at time t = 0?
Physics-Waves-96926.png
  • P
  • Q
  • R
  • S
A wave equation which gives the displacement along the Y direction is given by the equation y =104 sin (60t + 2x), where x and y are in metres and t is time in seconds. This represents a wave
  • Travelling with a velocity of 30 m/sec in the negative X direction
  • Of wavelength π metre
  • Of frequency 30/π Hz
  • Of amplitude 104 metre travelling along the negative X direction
  • All of the above
An air column in a pipe, which is closed at one end, will be in resonance with a vibrating tuning fork of frequency 264 Hz, if the length of the column in cm is
  • 31.25
  • 62.50
  • 93.75
  • 125
Velocity of sound in air is 320m/s. A pipe closed at one end has a length of 1m. Neglecting end corrections, the air column in the pipe can resonate for sound of frequency
  • 80 Hz
  • 240 Hz
  • 320 Hz
  • 400 Hz

Physics-Waves-96931.png
  • A wave travelling in the positive X direction with a velocity of 1.5 m/sec
  • A wave travelling in the negative X direction with a velocity of 1.5 m/sec
  • A wave travelling in the negative X direction with a wavelength of 0.2 m
  • A wave travelling in the positive X direction with a wavelength of 0.2 m
A sound wave of frequency v travels horizontally to the right. It is reflected from a large vertical plane surface moving to the left with a speed v. The speed of sound in the medium is c, then

  • Physics-Waves-96933.png
  • 2)
    Physics-Waves-96934.png

  • Physics-Waves-96935.png

  • Physics-Waves-96936.png

Physics-Waves-96938.png
  • A displacement node occurs a x = 0.15 m
  • An antinodes occurs at x = 0.3 m
  • The wavelength of the wave is 0.2 m
  • The speed of the wave is 5.0 m/s
The (x, y) coordinates of the corners of a square plate are (0, 0), (L, 0), (L, L) and (0, L). The edges of the plate are clamped and transverse standing waves are set up in it. If u(x, y) denotes the displacement of the plate at the point (x, y) at some instant of time, the possible expression(s) for u is(are) (a = positive constant)

  • Physics-Waves-96940.png
  • 2)
    Physics-Waves-96941.png

  • Physics-Waves-96942.png

  • Physics-Waves-96943.png
A transverse sinusoidal wave of amplitude a, wavelength λ, and frequency n is travelling on a stretched string. The maximum speed of any point on the string is v/10, where v is the speed of propagation of the wave. If a =10–3 m and v = 10 ms–1, then λ and n are given by

  • Physics-Waves-96945.png
  • 2)
    Physics-Waves-96946.png

  • Physics-Waves-96947.png

  • Physics-Waves-96948.png
As a wave propagates
  • The wave intensity remains constant for a plane wave
  • The wave intensity decreases as the inverse of the distance from the source for a spherical wave
  • The wave intensity decreases as the inverse square of the distance from the source for a spherical wave
  • Total intensity of the spherical wave over the spherical surface centered at the source remains constant at all times

Physics-Waves-96951.png
  • Pulse is moving in positive x-direction
  • In 2 s it will travel a distance of 2.5 m
  • Its maximum displacement is 0.16 m
  • It is a symmetric pulse
In a wave motion y = a sin (kx – ωt), y can represent
  • Electric field
  • Magnetic field
  • Displacement
  • Pressure
Standing waves can be produced
  • On a string clamped at both the ends
  • On a string clamped at one end and free at the other
  • When incident waves gets reflected from a wall
  • When two identical waves with a phase difference of 11 are moving in the same direction
The intensity of a progressing plane wave in loss-free medium is
  • Directly proportional to the square of amplitude of the wave
  • Directly proportional to the velocity of the wave
  • Directly proportional to the square of frequency of the wave
  • Inversely proportional to the density of the medium
It is desired to increase the fundamental resonance frequency in a tube which is closed at one end. This can be achieved by
  • Replacing the air in the tube by hydrogen gas
  • Increasing the length of the tube
  • Decreasing the length of the tube
  • Opening the closed end of the tube
The displacement of a particle in string stretched in X direction is represented by y. Among the following expressions for y, those describing wave motions are
  • cos kx sin ωt
  • k2x2 – ω2t2
  • cos (kx + ωt)
  • cos (k2x2 – ω2t2)
A student performed the experiment to measure the speed of sound in air using resonance air-column method. Two resonances in the air-column were obtained by lowering the water level. The resonance with the shorter air-column is the first resonance and that with the longer air-column is the second resonance. Then,
  • The intensity of the sound heard at the first resonance was more than that at the second resonance
  • The prongs of the tuning fork were kept in a horizontal plane above the resonance tube
  • The amplitude of vibration of the ends of the prongs is typically around 1 cm
  • The length of the air-column at the first resonance was somewhat shorter than 1/4th of the wavelength of the sound in air
A-person blows into open-end of a long pipe. As a result, a high-pressure pulse of air travels down the pipe. When this pulse reaches the other end of the pipe.
  • A high-pressure pulse starts travelling up the pipe, if the other end of the pipe is open
  • A low-pressure pulse starts travelling up the pipe, if the other end of the pipe is open
  • A low-pressure pulse starts travelling up the pipe, if the other end of the pipe is closed
  • A high-pressure pulse starts travelling up the pipe, if the other end of the pipe is closed
0:0:1


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