Untitled Document

Question Bank No: 1

1. A heavy uniform rope hangs vertically from the ceiling, with its lower end free. A distance on the rope travelling upwards from the lower end has a velocity V at a distance X from the lower end such that

a)		V $\times X$
b)		V $\times \sqrt{X}$
c)		V $\times \frac{1}{X}$
d)		V $\times \frac{1}{\sqrt{X}}$

2. If the tension and diameter of a sonometer wire of fundamental frequency n are doubled and density is halfed, then the fundamental frequency will become

a)		n/4
b)		$\sqrt{2} n$
c)		n
d)		n/ $\sqrt{2}$

3. The relation between phase difference and path difference is

a)		$Δ φ = \frac{2 π}{λ} (Δ x)$
b)		$Δ φ = 2 π λ Δ x$
c)		$Δ φ = \frac{2 π λ}{Δ x}$
d)		$Δ φ = \frac{2 Δ x}{λ}$

4. Ordinary conversation has an intensity of $10^{- 6} watt / m^{2},$ the noise level of conversation in dB is

a)		60dB
b)		1dB
c)		12dB
d)		6dB

5. An open organ pipe has fundamental frequency 100HZ. What frequencies will be produced if its one end is closed?

a)		100,200,300,-----
b)		50,150,250,-----
c)		50,100,200,300,----------
d)		50,100,150,200,-------

6. A wave travelling along a stretched string is represented by y = 3 Cos $π (100 t - x)$ its wave length is

a)		3 cm
b)		100cm
c)		2 cm
d)		5cm

7. A string in a musical instrument is 50cm long and its fundamental frequency is 800HZ. If a frequency of 1000HZ is to be produced then the required length of string is

a)		62.5cm
b)		50 cm
c)		40 cm
d)		37.5 cm

8. Two SHM of same amplitude, same frequency and phase difference of $Π / 4$ are superimposed at right angles to each other on a particle. The particle will describe

a)		circle
b)		ellipse
c)		figure of eight
d)		straight line

9. A wave travelling in a stretched string is described by the equation y = A sin(kx-wt). The maximum particle velocity is

a)		Aw
b)		w/k
c)		dw/dk
d)		x/t

10. The distance between two points differing in phase by $60^{0}$ on a wave having a wave velocity 360m/s and frequency 500HZ is

a)		0.72m
b)		0.12m
c)		0.18m
d)		0.36m

11. An echo repeats two syllables. If the velocity of sound is 330m/s. Then the distance of reflecting surface is

a)		66m
b)		33m
c)		99m
d)		16.5m

12. In ordinary talk, the amplitude of vibration is approximately

a)		$10^{- 12} m$
b)		$10^{- 11} m$
c)		$10^{- 8} m$
d)		$10^{- 7} m$

13. A wave is represented by x = 0.4 cos(8t-y/2) where x and y are in metres and tin seconds. The frequency of the wave is

a)		$\frac{4}{π} \sec^{- 1}$
b)		$\frac{8}{π} \sec^{- 1}$
c)		$\frac{5}{π} \sec^{- 1}$
d)		$\frac{6}{π} \sec^{- 1}$

14. The wave length of infrasonics in air is of the order of

a)		$10^{0} m$
b)		$10^{1} m$
c)		$10^{- 1} m$
d)		$10^{- 2} m$

15. With decrease in water vapour content in air, the velocity of sound

a)		increases
b)		decreases
c)		remains constant
d)		can't say

16. A source of sound emitting a tone of frequency 200Hz moves towards an observes with a velocity v equal to the velocity of sound. If the observer also moves away from the source with the same velocity v, the apparent frequency heared by the observes is

a)		50Hz
b)		100Hz
c)		150Hz
d)		200Hz

17. When the string of a sonometer of length L bewteen the bridges vibrates in the second overtone, The amplitude of vibration is maximum at

a)		L/2
b)		L/4 and 3L/4
c)		L/6, 3L/6 and 5L/6
d)		L/8,3L/8,5L/8,7L/8

18. A long glass tube is held vertically in water.A tuning fork is struck and held over the tube. Strong resonances are observed at two sucessive lengths 0.50m and 0.84m above the surface of water. If the velocity of sound is 340 m/s, then the frequency of the tuning fork is

a)		128Hz
b)		256 Hz
c)		384 Hz
d)		500Hz

19. A loaded string of length one metre and weighing 0.05g is hanging from a tuning fork of frequency 200Hz and is vibrating in four loops. For the transverse arrangement, the tension is

a)		1.25 $\times 10^{5} dynes$
b)		2.5 $\times 10^{5} dynes$
c)		5 $\times 10^{5} dynes$
d)		10 $\times 10^{5} dynes$

20. A tuning fork of frequency n is held near the open end of a tube which is closed at the other end and the length of the tube is adjusted until resonance occurs. If the two shortest lengths that produce resonance are $l_{1} and l_{2}$ the speed of the sound is

a)		n( $l_{2} - l_{1}$ )
b)		n(( $l_{2} - l_{1}$ )/2
c)		2n(( $l_{2} + l_{1}$ )
d)		2n(( $l_{2} - l_{1}$ )

21. A sonometer wire, 100cm in length has a fundamental frequency of 330Hz. The velocity of propagation of transverse waves along the wire is

a)		330 m/s
b)		660m/s
c)		115m/s
d)		990m/s

22. 56 tuning forks are so arranged in series that each tuning fork gives 4 beats per sec with the previous one. The frequency of the last fork is 3 times that of the first. The frequency of the first fork is

a)		110
b)		56
c)		66
d)		52

23. If the temperature is raised by 1 K from 300K the percentage change in the speed of sound in the gaseous mixture is (R=8.31J/mole-K)

a)		0.167%
b)		2%
c)		1%
d)		0.334%

24. A sound wave travelling with a velocity v in a medium A reaches a point on the interface of medium A and medium B. If the velocity in the medium B be 2v, the angle of incidence for total interval reflection of the wave will be

a)		$> 15^{0}$
b)		$> 30^{0}$
c)		$> 45^{0}$
d)		$> 90^{0}$

25. Three waves of equal frequencies having amplitudes 10 $μ m and 4 μ m and 7 μ m arrive at a given point with successive phase difference of π / 2. The amplitude of the resulting wave in μ m is given by$

a)		7
b)		6
c)		5
d)		4

26. A progressive wave frequency 500Hz is travelling with a velocity of 360m/s. How far apart are two points $60^{0} out of phase ?$

a)		1.2cm
b)		0.12cm
c)		120cm
d)		12cm

27. A light pointer fixed to one prong of a tuning fork touches a verticle plate. The fork is set vibrating and the plate is allowed to fall freely. Eight complete oscillations are counted when the plate falls through 10 cm. What is the frequency of tuning fork?

a)		112Hz
b)		56Hz
c)		$\frac{8}{7} Hz$
d)		$\frac{7}{8} Hz$

28. Two particles P and Q describe S.H.M of same amplitude a and frequency v along the same straight line. The maximum distance between two particles is a $\sqrt{2.}$ The initial phase difference between the particles is

a)		$π / 3$
b)		$π / 6$
c)		$π / 2$
d)		zero

29. A string of mass 0.2kg/m has length l=0.6m. It is fixed at both ends and stretched such that it has a tension of 80N. The string vibrates in three segments with amplitude =0.5cm. The amplitude of transverse velocity is

a)		9.42m/s
b)		3.14m/s
c)		1.57m/s
d)		6.28m/s

30. When a stretched wire and tuning fork are sounded together 5 beats per second are produced, when length of wire is 95cm or 100 cm. Frequency of fork is

a)		90
b)		100
c)		105
d)		195

31. Fundamental frequency of sonometer wire is n. If the length, tension and diameter of wire are tripled, the new fundamental frequency is

a)		$\frac{n}{\sqrt{3}}$
b)		$\frac{n}{3}$
c)		n $\sqrt{2}$
d)		$\frac{n}{3 \sqrt{3}}$

32. If the pressure amplitude in a sound wave is tripled, then the intensity of sound is increased by a factor

a)		3
b)		6
c)		9
d)		$\sqrt{3}$

33. The intensity of a sound wave gets reduced by 20% on passing through a slab. The reduction in intensity on passage through two such consecutive slabs is

a)		40%
b)		36%
c)		30%
d)		50%

34. The fundamental frequency of a sonometer wire carrying a block of mass 1 kg and density 1.8 is 260. When the block is completely immersed in a liquid of density 1.2 then what will be its new frequency ?

a)		300 Hz
b)		150 Hz
c)		450 Hz
d)		None of these

35. A uniform wire 20 metre long and weighing 50 newton hangs vertically. If g = 10 m/ $s^{2}$ then the speed of the transverse wave at the middle point of the wire is

a)		4 m/s
b)		10 $\sqrt{2}$ m/s
c)		10 m/s
d)		zero m/s

36. The end correction of a resonance column is 1.0 cm. If the shortest length resonating with a tuning fork is 15.0 cm, the next resonating length is

a)		31 cm
b)		45 cm
c)		46 cm
d)		47 cm

37. A tuning fork is found to give five beats in three seconds when sounded in conjunction with a stretched string vibrating transversely under a tension of either 10.2 kgf or 9.9 kgf. The frequency of the fork is approximately

a)		237 Hz
b)		235 Hz
c)		223 Hz
d)		225 Hz

38. A stretched string instead of being plucked in the middle is plucked at a point ${(1 / 4)}^{th}$ of its length from either of its ends. The frequency of vibration would be

a)		four times when plucked in the middle
b)		twice when plucked in the middle
c)		eight times when plucked in the middle
d)		same as when plucked in the middle

39. When two coherent waves interfere, there is

a)		loss in energy
b)		gain in energy
c)		redistribution of energy which changes with time
d)		redistribution of energy which does not changes with time

40. A student sees a jet plane flying from east to west. When the jet is seen just above his head, the sound of jet appears to reach him making angle $60^{o}$ with the horizontal from east. If the velocity of sound is v, then the velocity of the jet plane should be

a)		2v
b)		v $\sqrt{3}$
c)		$\sqrt{3} v$
d)		v

41. A small piece of cork in a ripple tank oscillates up and down as ripple pass it. If the ripples traveling at 0.3 m/s have a wavelength of 1.5 $π$ cm and the cork vibrates with an a,plitude of 5 mm, the maximum velocity of the cork is

a)		20 cm/ sec
b)		20 m/ sec
c)		0.02 m/ sec
d)		200 cm/ sec

42. It is possible to distinguish between transverse and longitudinal waves by studying the property of

a)		interference
b)		diffraction
c)		reflection
d)		polarization

43. An aeroplane is above the head of an observer and the sound appears to be coming at an angle of $60^{o}$ with the vertical. If velocity of sound is v, then the speed of aeroplane is

a)		v
b)		$\frac{\sqrt{3}}{2}$ v
c)		$\frac{v}{2}$
d)		2v

44. Equations of two progressive waves at a certain point in a medium are given by
$y_{1} = a \sin (ω t + φ_{1})$
and $y_{2} = a \sin (ω t + φ)$
If amplitude and time period of resultant wave formed by the super position of these two waves are same as those of either wave then ( $φ_{1} - φ_{2}$ ) is

a)		$π / 3$
b)		$π / 6$
c)		$π / 4$
d)		$2 π / 3$

45. A particle has displacement y given by
y = 3 sin (5 $π t + φ$ )
Where y is in metre and t is in second. What are frequency and period of motion?

a)		0.4 Hz, 2.5 s
b)		2.5 Hz, 0.4 s
c)		2.5 Hz, 2.5 s
d)		0.4 Hz, 0.4 s

46. A car sounding its horn at 480 Hz moves towards a high wall at a speed of 20 m/s. If the speed of the reflected sound heard by the man sitting in the car will be nearest to

a)		480 Hz
b)		510 Hz
c)		540 Hz
d)		570 Hz

47. The equation of a wave is represented by
y = $10^{- 4}$ sin $(100 t - \frac{x}{10})$ m
then the velocity of wave will be

a)		100 m/s
b)		4 m/s
c)		1000 m/s
d)		10 m/s

48. Sound waves of wavelength greater than that of audible sound are called

a)		Ultra sonic waves
b)		Sonic waves
c)		Seismic waves
d)		Infra sonic waves

49. Two sound waves of relative intensity 400:1 show interface. The ratio of intensity at the maximum to minima is close to

a)		$\frac{11}{9}$
b)		$\frac{401}{3900}$
c)		$\frac{21}{9}$
d)		$\sqrt{\frac{40}{399}}$