JEE Questions for Physics Waves Quiz 14 - MCQExams.com

A bus is moving with a velocity of 5 m/s towards a huge wall. The driver sounds a horn of frequency 165 Hz. If the speed of sound in air is 355 m/s, the number of beats heard per second by a passenger on the bus will be
  • 6
  • 5
  • 3
  • 4
A small source of sound moves on a circle as shown in the figure and an observer is standing on O . Let n1, n2 and n3 be the frequencies heard when the source is at A, B and C respectively. Then
Physics-Waves-96778.png
  • n1 > n2 > n3
  • n2 > n3 > n1
  • n1 = n2 > n3
  • n2 > n1 > n3
A source emits a sound of frequency of 400 Hz, but the listener hears it to be 390 Hz. Then
  • The listener is moving towards the source
  • The source is moving towards the listener
  • The listener is moving away from the source
  • The listener has a defective ear
A source and an observer are moving towards each other with a speed equal to v/2 where v is the speed of sound. The source is emitting sound of frequency n. The frequency heard by the observer will be
  • Zero
  • n

  • Physics-Waves-96780.png
  • 3n
A police car horn emits a sound at a frequency 240 Hz when the car is at rest. If the speed of the sound is 330 m/s, the frequency heard by an observer who is approaching the car at a speed of 11 m/s, is :
  • 248 Hz
  • 244 Hz
  • 240 Hz
  • 230 Hz
A person carrying a whistle emitting continuously a note of 272 Hz is running towards a reflecting surface with a speed of 18 km/hour. The speed of sound in air is 345 ms–1. The number of beats heard by him is
  • 4
  • 6
  • 8
  • 3
The speed of sound in air is 340 m/s. The speed with which a source of sound should move towards a stationary observer so that the apparent frequency becomes twice of the original
  • 640 m/s
  • 340 m/s
  • 170 m/s
  • 85 m/s
A bat flies at a steady speed of 4 ms–1 emitting a sound of f = 90 × 103 Hz. It is flying horizontally towards a vertical wall. The frequency of the reflected sound as detected by the bat will be (Take velocity of sound in air as 330 ms–1).
  • 88.1 × 103 Hz
  • 87.1 × 10–3 Hz
  • 92.1 × 103 Hz
  • 89.1 × 103 Hz
A source of sound is approaching an observer with speed of 30 ms–1 and the observer is approaching the source with a speed 60 ms–1. Then the fractional change in the frequency of sound in air (330 ms–1) is

  • Physics-Waves-96786.png
  • 2)
    Physics-Waves-96787.png

  • Physics-Waves-96788.png

  • Physics-Waves-96789.png
A police car with a siren of frequency 8 kHz is moving with uniform velocity 36 km/hr towards a tall building which reflects the sound waves. The speed of sound in air is 320 m/s. The frequency of the siren heard by the car driver is
  • 8.50 kHz
  • 8.25 kHz
  • 7.75 kHz
  • 7.50 kHz
A source is moving towards a stationary observer, so that the apparent frequency increases by 50%. If velocity of sound is 330 ms–1, then velocity of source is
  • 220 ms–1
  • 180 ms–1
  • 150 ms–1
  • 110 ms–1
If the amplitude of sound is doubled and the frequency reduced to one-fourth, the intensity of sound at the same point will be
  • Increased by a factor of 2
  • Decreased by a factor of 2
  • Decreased by a factor of 4
  • Unchanged

Physics-Waves-96793.png
  • 3000
  • 1000
  • 300
  • 30
Quality of a musical note depends on
  • Harmonics present
  • Amplitude of the wave
  • Fundamental frequency
  • Velocity of sound in the medium
A man x can hear only upto 10 kHz and another man y upto 20 kHz. A note of frequency 500 Hz is produced before them from a stretched string. Then
  • Both will hear sounds of same pitch but different quality
  • Both will hear sounds of different pitch but same quality
  • Both will hear sounds of different pitch and different quality
  • Both will hear sounds of same pitch and same quality
The amplitude of two waves are in ratio 5 : 2. If all other conditions for the two waves are same, then what is the ratio of their energy densities?
  • 5 : 2
  • 10 : 4
  • 2.5 : 1
  • 25 : 4
The loudness and pitch of a sound depends on
  • Intensity and velocity
  • Frequency and velocity
  • Intensity and frequency
  • Frequency and number of harmonics
If T is the reverberation time of an auditorium of volume V then

  • Physics-Waves-96796.png
  • 2)
    Physics-Waves-96797.png

  • Physics-Waves-96798.png

  • Physics-Waves-96799.png
The intensity of sound wave while passing through an elastic medium falls down by 10% as it covers one metre distance through the medium. If the initial intensity of the sound wave was 100 decibels, its value after it has passed through 3 metre thickness of the medium will be
  • 70 decibel
  • 72.9 decibel
  • 81 decibel
  • 60 decibel
Two waves having sinusoidal waveforms have different wavelengths and different amplitude. They will be having
  • Same pitch and different intensity
  • Same quality and different intensity
  • Different quality and different intensity
  • Same quality and different pitch
Intensity level 200 cm from a source of sound is 80 dB. If there is no loss of acoustic power in air and intensity of threshold hearing is 10–12 Wm–2 then, what is the intensity level at a distance of 4000 cm from source
  • Zero
  • 54 dB
  • 64 dB
  • 44 dB
In the musical octave `Sa\', \'Re\', \'Ga\'
  • The frequency of the note `Sa' is greater than that of 'Re', 'Ga'
  • The frequency of the note `Sa' is smaller than that of 'Re', 'Ga'
  • The frequency of all the notes `Sa', 'Re', 'Ga' is the same
  • The frequency decreases in the sequence `Sa', 'Re', 'Ga'
Learned Indian classical vocalists do not like the accompaniment of a harmonium because
  • Intensity of the notes of the harmonium is too large
  • Notes of the harmonium are too shrill
  • Diatonic scale is used in the harmonium
  • Tempered scale is used in the harmonium
Each of the properties of sound listed in column A primarily depends on one of the quantities in column B. Choose the matching pairs from two columns
Physics-Waves-96806.png
  • Pitch-Waveform, Quality-Frequency; Loudness-Intensity
  • Pitch-Frequency Quality-Waveform; Loudness-Intensity
  • Pitch-Intensity, Quality-Waveform; Loudness-Frequency
  • Pitch-Waveform, Quality- Intensity; Loudness-Frequency
A hollow pipe of length 0.8 m is closed at one end. At its open end a 0.5 m long uniform string is vibrating in its second harmonic and it resonates with the fundamental frequency of the pipe. If the tension in the wire is 50 N and the speed of sound is 320 ms–1, the mass of the string is
  • 5 grams
  • 10 grams
  • 20 grams
  • 40 grams

Physics-Waves-96808.png

  • Physics-Waves-96809.png
  • 2)
    Physics-Waves-96810.png

  • Physics-Waves-96811.png

  • Physics-Waves-96812.png
The ends of a stretched wire of length L are fixed at x = 0 and x = L. In one experiment, the displacement of the wire is y1 = A sin (πx / L) sin ωt and energy is E1, and in another experiment its displacement is y2 = A sin (2πx / L) sin 2ωt and energy is E2. Then
  • E2 = E1
  • E2 = 2E1
  • E2 = 4E1
  • E2 = 16E2
In a large room, a person receives direct sound waves from a source 120 metres away from him. He also receives waves from the same source which reach him, being reflected from the 25 metre high ceiling at a point halfway between them. The two waves interfere constructively for wavelength of
  • 20, 20/3, 20/5 etc
  • 10, 5, 2.5 etc
  • 10, 20, 30 etc
  • 15, 25, 35 etc
A train has just completed a U-curve in a track which is a semicircle. The engine is at the forward end of the semi circular part of the track while the last carriage is at the rear end of the semicircular track. The driver blows a whistle of frequency 200 Hz. Velocity of sound is 340 m/sec. Then the apparent frequency as observed by a passenger in the middle of a train when the speed of the train is 30 m/sec is
Physics-Waves-96816.png
  • 209 Hz
  • 288 Hz
  • 200 Hz
  • 181 Hz
Two identical flutes produce fundamental notes of frequency 300 Hz at 27°C. If the temperature of air in one flute is increased to 31°C, the number of the beats heard per second will be
  • 1
  • 2
  • 3
  • 4
In the experiment for the determination of the speed of sound in air using the resonance column method, the length of the air column that resonates in the fundamental mode, with a tuning fork is 0.1 m. When this length is changed to 0.35 m, the same tuning fork resonates with the first overtone. Calculate the end correction
  • 0.012 m
  • 0.025m
  • 0.05 m
  • 0.024m
A closed organ pipe of length L and an open organ pipe contain gases of densities ρ1 and ρ2 respectively. The compressibility of gases are equal in both the pipes. Both the pipes are vibrating in their first overtone with same frequency. The length of the open organ pipe is

  • Physics-Waves-96820.png
  • 2)
    Physics-Waves-96821.png

  • Physics-Waves-96822.png

  • Physics-Waves-96823.png
A string of length 0.4 m and mass 10–2 kg is tightly clamped at its ends. The tension in the string is 1.6 N. Identical wave pulses are produced at one end at equal intervals of time ∆t. The minimum value of ∆t which allows constructive interference between successive pulses is
  • 0.05 s
  • 0.10 s
  • 0.20 s
  • 0.40 s
Two identical stringed instruments have frequency 100 Hz. If tension in one of them is increased by 4% and they are sounded together then the number of beats in one second is
  • 1
  • 8
  • 4
  • 2
The difference between the apparent frequency of a source of sound as perceived by an observer during its approach and recession is 2% of the natural frequency of the source. If the velocity of sound in air is 300 m/sec, the velocity of the source is (It is given that velocity of source < < velocity of sound)
  • 6 m/sec
  • 3 m/sec
  • 1.5 m/sec
  • 12 m/sec
A plane EM wave of frequency 30 MHz travels in free space along the x-direction. The electric field component of the wave at a particular point of space and time E = 6V/m along y-direction. Its magnetic field component B at this point would be
  • 2 × 10–8 T along z-direction
  • 6 × 10–6 T along x-direction
  • 2 × 10–8 T along y-direction
  • 6 × 10–8 T along z-direction
Two cars are moving on two perpendicular roads towards a crossing with uniform speeds of 72 km/hr and 36 km/hr. If first car blows horn of frequency 280 Hz, then the frequency of horn heard by the driver of second car when line joining the cars make 45° angle with the roads; will be
  • 321 Hz
  • 298 Hz
  • 289 Hz
  • 280 Hz
Two whistles A and B produce notes of frequencies 660 Hz and 596 Hz respectively. There is a listener at the mid-point of the line joining them. Now the whistle B and the listener start moving with speed 30 m/s away from the whistle A. If speed of sound be 330 m/s, how many beats will be heard by the listener?
  • 2
  • 4
  • 6
  • 8
A source producing sound of frequency 170 Hz is approaching a stationary observer with a velocity 17 ms–1. The apparent change in the wavelength of sound heard by the observer is (speed of sound in air = 340 ms–1 )
  • 0.1 m
  • 0.2 m
  • 0.4 m
  • 0.5 m
A police car moving at 22 m/s, chases a motorcyclist. The police man sounds his horn at 176 Hz, while both of them move towards a stationary siren of frequency 165 Hz. Calculate the speed of the motorcycle, if it is given that he does not observes any beats
Physics-Waves-96832.png
  • 33 m/s
  • 22 m/s
  • Zero
  • 11 m/s
A light pointer fixed to one prong of a tuning fork touches a vertical plate. The fork is set vibrating and the plate is allowed to fall freely. If eight oscillations are counted when the plate falls through 10 cm, the frequency of the tuning fork is
  • 360 Hz
  • 280 Hz
  • 560 Hz
  • 56 Hz
Oxygen is 16 times heavier than hydrogen. Equal volumes of hydrogen and oxygen are mixed. The ratio of speed of sound in the mixture to that in hydrogen is

  • Physics-Waves-96835.png
  • 2)
    Physics-Waves-96836.png

  • Physics-Waves-96837.png

  • Physics-Waves-96838.png

Physics-Waves-96840.png
  • Amplitude A/2, frequency 2n and wavelength λ/2
  • Amplitude A/2, frequency 2n and wavelength λ
  • Amplitude A, frequency 2n and wavelength 2 λ
  • Amplitude A, frequency n and wavelength λ
If the length of a closed organ pipe is lm and velocity of sound is 330 m/s, then the frequency for the second note is

  • Physics-Waves-97030.png
  • 2)
    Physics-Waves-97031.png

  • Physics-Waves-97032.png

  • Physics-Waves-97033.png
Consider ten identical sources of sound all giving the same frequency but having phase angles which are random. If the average intensity of each source is I0, the average of resultant intensity I due to all these ten sources will be
  • I = 100 I0
  • I = 10 I0
  • I = I0

  • Physics-Waves-96842.png
Ten tuning forks are arranged in increasing order of frequency in such a way that any two nearest tuning forks produce 4 beats/sec. The highest frequency is twice of the lowest. Possible highest and the lowest frequencies are
  • 80 and 40
  • 100 and 50
  • 44 and 22
  • 72 and 36
41 forks are so arranged that each produces 5 beats per sec when sounded with its near fork. If the frequency of last fork is double the frequency of first fork, then the frequencies of the first and last fork are respectively
  • 200,400
  • 205,410
  • 195,390
  • 100,200
Two identical wires have the same fundamental frequency of 400 Hz when kept under the same tension. If the tension in one wire is increased by 2% the number of beats produced will be
  • 4
  • 2
  • 8
  • 1
25 tuning forks are arranged in series in the order of decreasing frequency. Any two successive forks produce 3 beats/sec. If the frequency of the first tuning fork is the octave of the last fork, then the frequency of the 21st fork is
  • 72 Hz
  • 288 Hz
  • 84 Hz
  • 87 Hz
The frequency of a stretched uniform wire under tension is in resonance with the fundamental frequency of a closed tube. If the tension in the wire is increased by 8 N, it is in resonance with the first overtone of the closed tube. The initial tension in the wire is
  • I N
  • 4 N
  • 8 N
  • 16 N
0:0:1


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