Title WAVES.pdf ✅

15.WAVES Single Correct Answer Type 1. A police car moving at22 ms , changes a motorcyclist. The police man sounds his horn at 176 Hz, while −1 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 observe any beats. a) 33ms −1 b) 22 ms −1 c) Zero d) 11ms −1 2. 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 a) L 2 L 2+l 2 b) L 2−l 2 L 2 c) L 2 L 2−l 2 d) L 2+l 2 L 2 3. A man standing between two parallel hills, claps his hand and hears successive echoes at regular intervals of 11s. If velocity of sound is 340ms then the distance between the hills is −1 , a) 100m b) 170 m c) 510 m d) 340 m 4. The disc of a siren containing 60 holes rotates at a constant speed of 360 rpm. The emitted sound is in unison with a tuning fork of frequency a) 10 Hz b) 360 Hz c) 216 Hz d) 60 Hz 5. A wire of density 9×10 is stretched between two clamps 1m part and is subjected to an extension 3 kgm −3 of4. 9×10 . The lowest frequency of transverse vibration in the wire is −4 m Y = 9×10 10Nm −2 ) a) 40 Hz b) 35 Hz c) 30 Hz d) 25 Hz 6. A piston fitted in cylindrical pipe is pulled as shown in the figure. A tuning fork is sounded at open end and loudest sound is heard at open length 13cm, 41 cm and 69 cm, the frequency of tuning fork if velocity of sound is 350ms is −1 a) 1250 Hz b) 625 Hz c) 417 Hz d) 715 Hz 7. Quality of a musical note depends on a) Harmonics present b) Amplitude of the wave Page| 1
c) Fundamental frequency d) Velocity of sound in the medium 8. A 5.5 m length of string has a mass of 0.035 kg. If the tension in the string is 77 N, the speed of a wave on the string is a) 110ms −1 b) 165m −1 c) 77ms −1 d) 102ms −1 9. When an aeroplane attains a speed higher than the velocity of sound in air, a loud bang is heard. This is because a) It explodes b) It produces a shock wave which is received as the bang c) Its wings vibrate so violently that the bang is heard d) The normal engine noises undergo a Doppler shift to generate the bang 10. A tuning fork of frequency 200 Hz is in unison with a sonometer wire. The number of beats heard per second when the tension is increased by 1% is a) 1 b) 2 c) 4 d) 1/2 11. The frequency and velocity of sound wave are 600 Hz and 360 m/s respectively. Phase difference between two particles of medium are 60°, the minimum distance between these two particles will be a) 10 cm b) 15 cm c) 20 cm d) 50 cm 12. An observer is standing 500 m away from a vertically hill. Starting between the observer and the hill a police van having a siren of frequency 1000 Hz moves towards the hill with a uniform speed. If the frequency of the sound heard directly from the siren is 970 Hz, the frequency of the sound heard after reflection from the hill (in Hz) is about, (velocity of sound =330 ms ) −1 a) 1042 b) 1032 c) 1022 d) 1012 13. An observer moves towards a stationary source of sound with a velocity one-fifth of the velocity of sound. What is the percentage increases in the apparent frequency? a) Zero b) 0.5% c) 5% d) 20% 14. With the propagation of a longitudinal wave through a material medium, the quantities transmitted in the propagation direction are a) Energy, momentum and mass b) Energy c) Energy and mass d) Energy and linear momentum 15. When a tuning fork vibrates, the waves produced in the fork are a) Longitudinal b) Transverse c) Progressive d) Stationary 16. A tuning fork of frequency 392 Hz, resonates with 50 cm length of a string under tension (T). If length of the string is decreased by 2%, keeping the tension constant, the number of beats heard when the string and the tuning fork made to vibrate simultaneously is a) 4 b) 6 c) 8 d) 12 17. A 1000 Hz sound wave in air strikes the surface of a lake and penetrates into water. If speed of sound in water is 1500ms ,the frequency and wavelength of waves in water are −1 a) 1500 Hz, 1m b) 1000 Hz, 1.5m c) 1000 Hz, 1m d) 1500 Hz, 1.5m 18. If in a resonance tube a oil of density higher than that water is used then at the resonance frequency would Page| 2
a) Increase b) Decrease c) Slightly increase d) Remain same 19. Three sources of equal intensities with frequencies 400, 401 and 402 vib/s are sounded together. The number of beats/s is a) Zero b) 1 c) 2 d) 4 20. Figure here shown an incident pulse P reflected from a rigid support. Which one of A, B, C, D represents the reflected pulse correctly a) b) c) d) 21. A cylindrical tube containing air is open at both ends. If the shortest length of the tube for resonance with a given fork is 2 cm, the next shortest length for resonance with the same fork will be a) 60 cm b) 40 cm c) 90 cm d) 80 cm 22. On which principle does sonometer works? a) Hooke’s law b) Elasticity c) Resonance d) Newton’s law 23. The intensity ratio of two waves is 1:9. The ratio of their amplitudes, is a) 3:1 b) 1:3 c) 1:9 d) 9:1 24. The driver of a car travelling with speed 30 metres per second towards a hill sounds a horn of frequency 600 Hz. If the velocity of sound in air is 330 metres per second, the frequency of the reflected sound as heard by the driver is a) 720 Hz b) 555. 5 Hz c) 550 Hz d) 500 Hz 25. The musical interval between two tones of frequencies 320 Hz and 240 Hz is a) 80 b) 4 ( 3 ) c) 560 d) 320×240 26. Two tuning fork, A and B produce notes of frequencies 258 Hz and 262 Hz. An unknown note sounded with a produces certain beats. When the same note is sounded with B, the beat frequency gets doubled, the unknown frequency is a) 256 Hz b) 254 Hz c) 300 Hz d) 280 Hz 27. 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? a) 5:2 b) 5:4 c) 4:5 d) 25:4 28. v and are the velocities of sound at the same temperature in two monoatomic gases of densities and 1 v 2 ρ 1 ρ respectively. If then the ratio of velocities and will be 2 ρ 1 /ρ 2 = 1 4 v 1 v 2 a) 1 : 2 b) 4 : 1 c) 2 : 1 d) 1 : 4 29. The equation y = A(2π nt − 2π represents a wave with x λ ) a) Amplitude A/2, frequency 2n and wavelength λ/2 b) Amplitude A/2, frequency 2n and wavelength λ Page| 3
c) Amplitude A, frequency 2n and wavelength 2λ d) Amplitude A, frequency n and wavelength λ 30. A wavelength 0. 60 cm is produced in air and it travels at a speed of 300 ms It will be an −1 . a) Audible wave b) Infrasonic wave c) Ultrasonic wave d) None of the above 31. The sound wave was produced in a gas is always a) Longitudinal b) Transverse c) Stationary d) Electromagnetic 32. Two Cu wires of radii R such that Then which of the following is true? 1 and R 2 R 1 > R 2 ( ). a) Transverse wave travels after in thicker wire b) Transverse wave travels faster in thinner wire c) Travels with the same speed in both the wires d) Does not travel 33. A police car horn emits a sound at a frequency 240 Hz the frequency 240 Hz when the car is at rest. If the speed of sound is 330ms , the frequency heard by an observer who is approaching the car at speed of 11 −1 ms , is −1 a) 248 Hz b) 244 Hz c) 240 Hz d) 230 Hz 34. The apparent frequency of the whistle of an engine changes in the ratio 9:8 as the engine passes a stationary observer. If the velocity of the sound is 340ms , then the velocity of the engine is −1 a) 40 ms −1 b) 20 ms −1 c) 340 ms −1 d) 180 ms −1 35. Two waves of frequencies 20 Hz and 30 Hz. Travels out from a common point. The phase difference between them after 0. 6 sec is a) Aero b) π 2 c) π d) 3π 2 36. The frequency of the fundamental note in a wire stretched under tension T is v. if the tension is increased to 25T, then the frequency of the fundamental note will be a) 25v b) 5v c) 10v d) V 37. Two stretched strings have length l and 2l while tensions are T and 4T respectively. If they are made of same material the ratio of their frequencies is a) 2:1 b) 1:2 c) 1:1 d) 1:4 38. The waves in which the particles of the medium vibrate in a direction perpendicular to the direction of wave motion is known as a) Transverse wave b) Longitudinal waves c) Propagated waves d) None of these 39. The equation of progressive wave isy = 0. 2 sin sin 2π , where x and y are in metre and t is in t 0.01 − x 0.3 ⎡ ⎣ ⎤ ⎦ second. The velocity of propagation of the wave is a) 30 ms −1 b) 40 ms −1 c) 300 ms −1 d) 400 ms −1 40. The phase difference between two points separated by 0.8 m in a wave of frequency 120 Hz is0. 5π. The wave velocity is a) 144ms −1 b) 384ms −1 c) 256ms −1 d) 720ms −1 Page| 4