Sound Waves Questions and Answers

c 75 ms 1 d 100 m s 72 A guitar string is 90 cm long and has a fundamental frequency of 124 Hz To produce a fundamental of 186 Hz the guitar should be pressed frequency a 60 cm b 30 cm c 20 cm d 10 cm 73 A stretched wire emits a fundamental note of 256 Hz and reducing 79 V n c 80 T a b

a 336 m s c 300 m s b 343 m s d 350 m st 75 Two pipes are each 50 cm in length One of them is closed at one end while the other is open at both ends The speed of sound in air is 340 ms The frequency at which both the pipes can resonate is a 680 Hz b 510 Hz c 85 Hz d none of these

320 Hz the original length of the wire is a 100 cm b 50 cm c 400 cm d 200 cm 4 A tuning fork of frequency 440 Hz resonates with a tube closed at one end of length 1 8 cm and diameter 5 cm in fundamental mode The velocity of sound in air is a 336 m s c 300 m s b 343 ms d 350 m s of them 81

frequency phase and amplitude 59 One of the modes of resonance in a tube containing water at one end has been shown The tube in the present case is in a first harmonic b third harmonic c fifth harmonic d seventh harmonic xXxxXxX 60 Two open organs pipes of fundamental frequencies and are joined in series The fundamental proc be a a 65 A s mic the Sp a c

cies ental a b u c 20 d 4u 65 A steel rod of length 100 cm is clamped at the middle The frequency of the fundamental mode for the longitudinal vibrations of the rod is Speed of sound in steel 5 km s a 1 5 kHz b 2 kHz d 3 kHz c 2 5 kHz

70 A resonating air column shows resonance with a tuning fork of frequency 256 Hz at column lengths 78 33 4 cm and 101 8 cm The speed of sound in air is a 300 m s b 250 m s c 390 m s d 350 m s thrtween two rigid supports vibrates

On sounding tuning fork A with another tuning fork B of frequency 384 Hz 6 beats are produced per second After loading the prongs of A with some wax and then sounding it again with B 4 beats are produced per second What is the frequency of the tuning fork A Question Type Single Correct Type 1 2 3 4 388 Hz 380 Hz 378 Hz 390 Hz

A musical note on a piano has a frequency of 45 Hz If the tension in the 2 m string is 308 N and one half wavelength occupies the string what is the mass of the wire O O O 0 019 kg 0 040 kg 0 031 kg 0 024 kg O 0 047 kg

Three sound waves of equal amplitudes have frequencies n 1 n n 1 They superimpose to give beats The number of beats produced per second will be a 1 c 3 b 4 d 2 NFFT I 2010

A body is walking away from a wall towards an observer at a speed of 2 m s and blows a whistle whose frequency is 660 Hz The number of beats heard by the observer per second is velocity of sound in air 330 m s

A sound source of constant frequency travels with a constant velocity past an observer When it crosses the observer the sound frequency sensed by the observer changes from 360 Hz to 320 Hz If the velocity of sound in 340 m s the velocity of the source of sound is 8 m s 12 m s 20 m s 14 m s

An air column open at one end resonates with a tuning fork when the smallest length of the column is 20 cm The next larger length of the column resonating with same tuning fork is 60 cm 90 cm 120 cm

4 y 10 14 A man standing between two cliffs claps his hands 19 Aarobserw D sound wit and starts hearing a series of echoes at intervals of 2 sec Since the speed of sound in air is 340 m sec The distance between the cliffs must be sound T 15 1 340 m 3 1020 m 2 680 m 4 170 m vibrator makes 150 cm of a string to vibrate in 6 loops in the longitudinal arrangement when it is ON The entire length of the string 20 zero A persc of sour towar 320 m appre 1

A man fires a bullet standing between two cliffs First echo is heard after 3 seconds and second echo is heard after 5 seconds If the velocity of sound is 330 m s then the distance between the cliffs is Question Type Single Correct Type 1 1650 m 2 1320 m 3 990 m

Ice and water are placed in a closed container at a pressure of 1 atm and 273 15 K temperature If press of the system is increased by 2 atm keeping temperature constant the correct observation would be 1 The liquid phase disappears completely 2 The amount of ice increases 3 The solid phase ice disappears completely 4 Volume of the system increases

1 what is the velocity of sound in glass tube if the glass tube is 4m 2 how do you compare velocity of sound and velocity of carbon dioxide using density 3 if a paper disc were not used at the end of the rode what will happen or change

10 Three sound sources are emitting waves of wavelength 6 cm such that source at A is lagging in phase by 3 from source at B Source at C is 3 phase ahead to source at B All are emitting waves producing same intensity I at point D A detector D as shown is at 4 cm distance from B on line perpendicular to ABC line and distance between successive sources is 2 Find the resultant intensity at D A 3cm B 3cm

5 An open organ pipe of length 1 is sounded together with another open organ pipe of length 1 x in their fundamental tones Speed of sound in air is v The beat frequency heard will be x 1 V 2x VX 4 a b c VX 21 d vx 21

6 Two sound sources are moving in opposite directions with velocities v and v v U Both are moving V1 away from a stationary observer The frequency of both the sources is 900 Hz What is the value of V V2 so that the beat frequency observed by the observer is 6 Hz Speed of sound v 300 m s Given that U1 and a 1 m s U v V2 b 2 m s c 3 m s d 4 m s

34 A source of frequency 10 kHz when vibrated over the mouth of a closed organ pipe is in unison at 300 K The beats produced when temperature rises by 1 K is a 30 Hz c 16 67 Hz 6 b 13 33 Hz d 40 Hz

Two tuning forks of frequency 250 Hz and 256 Hz produce beats If a maximum is observed just now after how much time the minimum is observed at the same place Question Type Single Correct Type 1 2 3 1 S 18 S 12

Erica listens to her headphones on full volume and it hurts her ears This is because the sound waves had too large of a n a Amplitude b Frequency Oc Wavelength d Resonance

57 Plane simple harmonic waves of wavelength 120 cm and speed 34000 cm sec are incident normally on a plane surface which is a perfect reflector of sound Stationary waves are formed The ratio of amplitudes of vibration at point distance 1 10 cms 2 30 cms from the reflector is 1 2 b1 4 1 1 1 3

41 Velocity of sound in an open organ pipe is 330 m s The frequency of wave is 1 1 kHz and the length of tube is 30 cm To which harmonic does this frequency corresponds a 2nd b 3rd c 4th d 5th

3 A sound wave of wavelength 40 cm travels in air If the difference between the maximum and minimum pressures at a given point is 10 x 10 Nm find the amplitude of vibration of the particles of the medium The bulk modulus of air is 1 4 x 105 Nm 2 Solution The pressure amplitude is 3 1 0 10 Nm 2 Po or The displacement amplitude so is given by Po B k so So Po Po Bk 2 T B 3 0 5 x 10 N m 40 10 m 2x3 14 x 14 x 105 Nm 2 2 2 x 10 0 5 10 Nm 10 m 10

40 A closed organ pipe and an open organ pipe of same length produce 2 beats when they are set into vibrations simultaneously in their fundamental mode The length of open organ pipe is now halved and of closed organ pipe is doubled the number of beats produced will be a 8 b 7 c 4 d 2

47 A steel rod 100 cm long is clamped at its centre The fundamental frequency of longitudinal vibrations of the rod are given to be 2 53 kHz What is the speed of sound in steel a 10 06 km s 1 c 15 06 km s 1 b 5 06 km s 1 d 2 42 km s 1

42 First overtone frequency of a closed organ pipe is equal to the first overtone frequency of an open organ pipe Further nth harmonic of closed organ pipe is also equal to the mth harmonic of open pipe where n and mare 0090psi is i svas a 5 4 b 7 5 b c 9 6 d 7 3

The sound waves after being converted into electrical waves are not transmitted as such because 1 They travel with the speed of sound 2 The frequency is not constant 3 They are highly absorbed by the atmosphere 4 The height of antenna has to be increased several times

15 A string fixed at both ends vibrates in a resonant mode with a separation of 2 0 cm between the consecutive nodes For the next higher resonant frequency this separation is reduced to 1 6 cm The length of the string is a 4 0 cm c 12 0 cm b 8 0 cm d 16 0 cm

39 A wave represented by the equation with another Y1 A cos kx wt is superimposed wave to form a stationary wave such that the point x 0 is a node The equation of the other wave is a y2 A sin kx wt b y A cos kx wt y2 c y A sin kx wt d y2 A cos kx wt

26 For a certain organ pipe three successive resonance frequencies are observed at 425 Hz 595 Hz and 765 Hz respectively If the speed of sound in air is 340 m s then the length of the pipe is a 2 0 m c 1 0 m b 0 4 m d 0 2 m

46 Equations of a stationary and a travelling waves are y a sin kx cos wt and y2 a sin wt kx The phase difference between two points x1 x2 3 are 1 and 2 respectively for the two waves 2k The ratio a 1 1 is 2 b 5 6 c 3 4 69 TC 3k d and

le ratio of intensities between two coherent sound sources is 4 1 The difference of loudness in decibel dB between maximum and minimum intensities when they interfere in space is letrar a 10 log 2 c 10 log 3 b 20 log 3 d 20 log 2

2 A closed organ pipe and an open organ pipe of same length produce four beats in their fundamental mode when sounded together If length of the open organ pipe is increased then the number of beats will a increase c remain constant b decrease d may increase or decrease

A man standing between two cliffs hears the first echo of a sound after 1 5 sec and the second echo 2 5 sec after the initial sound If the speed of sound be 330 m s the distance between the two cliffs should be Question Type Single Correct Type 1 1650 m 2 990 m 3 825 m 4 660 m

Speed of sound waves in a fluid depends upon Question Type Single Correct Type 1 Directly on density of the medium 2 Square of Bulk modulus of the medium 3 Directly on the square root of density 4 Directly on the square root of bulk modulus of

13 A person can hear frequencies only upto 10 kHz A steel piano wire 50 cm long of mass 5 g is stretched with a tension of 400 N The number of the highest overtone of the sound produced by this piano wire that the person can hear is a 48 c 49 b 50 d 51

6 The second overtone of an open pipe A and a closed pipe B have the same frequencies at a given temperature Both pipes contain air The ratio of fundamental frequency of A to the fundamental c 5 6 d 6 5 frequency a 3 5 of B is b 5 3

11 Two trains move towards each other with the same speed Speed of sound is 340 ms 1 If the frequency of the tone of the whistle of one when heard by the other changes by 9 8 times then the speed of each train is a 10 ms 1 c 20 ms 1 V 1 b 40 ms d 15 ms 1

14 Two corks are 10 m apart in a lake Each goes up and down with period 0 5s It is observed that when one is at its highest point other one is at lowest point The possible speed of wave is a 2 5 m s b 5 m s c 40 m s d 4 m s 20 A unif vertica attach wavel rope ton

Three one dimensional mechanical waves in an elastic medium are given as y 2A sin wt kx y 2A sin wt kx y3 2A sin wt kx 1 For any value of the 4 maximum displacement amplitude in cm of the medium particles would be Given A 1 cm Correct answer 6

The speed of a transverse wave in an elastic string is vo If the tension in the string is reduced to half then the speed of the wave is given by b v 2 a C Vo 2 Vo 2 d 2 vo

A siren generates a sound with a frequency of 250Hz but when you hear the siren traveling down the road you measure a frequency of 280Hz Which answer best explains why you detect a different frequency than what the siren generates O a Since the frequency of the siren is higher the source of the sound wave must be moving away from you b Since the frequency of the siren is higher the source of the sound wave must be moving towards you Oc There are no explanations for why you measured a higher frequency than expected d The driver of the vehicle increased the frequency with a controller

b 6 c 9 d Zero a 3 66 A stationary sound source of frequency 334 Hz and a stationary observer O are placed reflecting surface shown in figure Velocity of sound waves in air v 330 moving away from the source with velocity 2m s as m s The apparent frequency of echo is OS a 332 Hz b 326 Hz 2 m s c 334 Hz d 330 Hz 12 F toward is 330 m s standing behind 256 330 325 256 a b 256 256x330 325 256x33 325 C d 11 Doppler s

Plane harmonic waves of frequency 500 Hz500 Hz are produced in air with displacement amplitude of 10 m Given that density of air is and speed of sound in air is 340 m s Then A The pressure amplitude is 13 8 N m2 8 The energy density is 6 4 x 10 J m The energy flux is 0 22J m s The energy flux is 0 88J m s D

24 A dog is barking at a power of 40 mW Its intensity level of sound emitted at a distance 1 m from the dog is 1 90 dB 2 100 dB 3 120 dB 4 Zero Vo X 401 x 10 56011 AIX 5 lolog Jo lo

90 71 6 18 4 3 A string 2 0 m long and fixed at its ends is driven by a 240 Hz vibrator The string vibrates in i third harmonic mode The speed of the wave and its fundamental frequency is 1 320 m s 120 Hz 2 320 m s 80 Hz 3 180 ms 80 Hz 4 180 m s 120 Hz Key 2

Two students are participating in a lab where they make waves on a long spring One student starts by making 2 waves appear on the spring then gradually moves her hand at a faster rate in order to produce 4 waves on the spring Which answer best describes what the student changed about the wave on the spring a Since there are more waves occurring in the same space the frequency of the waves has increased while the wavelength of the wave decreased Ob Since there are more waves occurring in the same space the frequency of the waves has increased while the speed of the wave decreased c Since there are more waves occurring in the same space the wavelength of the waves has increased while the frequency of the wave decreased d Since there are more waves occurring in the same space the wavelength of the waves has increased while the speed of the wave decreased

F 74 A person P is 600 m away from the station when train is approaching station with 72 km h it blows a whistle of frequency 800 Hz when 800 m away from the station Find the frequency heard by the person Speed of sound 340 ms a 800 Hz c 829 5 Hz 800 m b 839 5 Hz d 843 5 Hz S 600 m P