PAST QUESTIONS OF CHAPTER – 8

FROM ALL PUNJAB BOARD PAPERS -2011-

2017
OBJECTIVE QUESTIONS
1. The value of “γ” for diatomic gas is:
(A) 1.67 (B) 1.40
(C) 1.29 (D) Infinity
2. Radar system is an application of: (3times)
(A) Inference (B) Beats
(C) Stationary waves (D) Doppler Effect
3. Longitudinal waves did not exhibit: (3times)
(A) Reflection (B) Refraction
(C) Diffraction (D) Polarization
4. 10 waves pass through the medium in one sec with speed of 10m/s. the
wavelength of waves is:
(A) 1m (B) 10m
(C) 20m (D) 100m
5. Distance between two consecutive nodes is: (5times)
λ
(A) λ (B) 4
λ
(C) 2 (D) 2 λ
6. Beats are used to find:
(A) Frequency (B) Wavelength
(C) Intensity (D) Speed

7. The speed of sound in air depends upon:

(A) Temperature (B) Humidity
(C) Density (D) All of these
8. Both transvers and longitudinal waves can be setup in which one of the following
media:
(A) Solid (B) Liquid
(C) Gas (D) Plasma
9. The speed of sound has maximum value in:
(A) Oxygen (B) Air
(C) Hydrogen (D) Helium
10. The wavelength of the fundamental mode of vibration of a pipe closed at one end
is:
ℓ
(A) 2 (B) ℓ
(C) 2ℓ (D) 4ℓ
11. Which electromagnetic waves are uses as medium in satellite communication
system:
(A) Microwaves (B) Radio waves
(C) Infrared waves (D) Ultraviolet waves
12. Sound waves cannot be:
(A) Reflection (B) Refraction
(C) Polarized (D) Diffraction
13. For each degree Celsius rise in temperature of gas, the speed of sound through it
increase by: (4times)
(A) 0.60 ms -1
(B) 0.61 ms-1
(C) 61 ms -1
(D) 6.1 ms-1
14. A horizontal pipe narrows from a diameter of 10cm to 5cm. for a fluid flowing larger
diameter to smaller:
(A) The velocity and pressure both increase (B) The velocity increase
and pressure decrease
(C) The velocity decrease and pressure increase (D) The velocity and pressure
both decrease
15. Which of the following does not have any effect on the speed of sound in gasses?
(A) Temperature (B) Density
Cp
γ=
(C)
Cv (D) Pressure
16. The louder the sound, the greater will be its:
(A) Amplitude (B) Wavelength
(C) Speed (D) Frequency
17. Two waves of equal frequency travelling in opposite direction produce:
(2itmes)
(A) Interference (B) Stationary waves
(C) Beats (D) Doppler Effect
18. The time period of a wave is 0.2 s. its frequency will be:
(A) 2 s (B) 0.4 s
(C) 0.5 s (D) 5 s-1
19. If the speed of sound in air at a given pressure is V, then by increasing pressure to
doubled, the new speed becomes:
(A) 0.5 V (B) V
(C) 2 V (D) 4 V
20. Two waves can interfere only if they have:
(A) Phase coherence (B) Same velocity
(C) Different frequencies (D) Different wavelength
21. In stationary wave one mode of vibration of the string having length ℓ is equal to:
(A) λ (B) λ/2
(C) λ/4 (D) 2λ
22. Electromagnetic wave travel in free space with velocity equal to:
(A) 3×106 ms−1 (B) 3×107 ms−1
8 −1 9 −1
(C) 3×10 ms (D) 3×10 ms
23. Appropriate range of audible frequency for younger person is:
(A) 20-200Hz (B) 20-2000Hz
(C) 20-20000Hz (D) 2000-20000Hz
24. For same mass and length if tension of a vibrating string is increase four times the
speed of wave increased by:
(A) 6 times (B) 4 times
(C) 8 times (D) 2 times
25. Beats detectable easily up to frequency different between two sound is:
(A) 2 Hz (B) 6 Hz
 (C) 10 Hz (D) 32 Hz
26. Star moving away from the earth shows:
(A) Red shift (B) Blue shift
(C) Doppler’s shift (D) Frequency shift
27. Velocity of sound in free space at 0oC:
(A) 332 ms-1 (B) 224 ms-1
(C) 76 ms -1
(D) 0
28. The number of anti-node between two nodes is:
(A) 1 (B) 2
(C) 3 (D) 4
29. The frequency of waves produce in microwave oven is:
(A) 1450 MHz (B) 1650 MHz
(C) 2450 MHz (D) 2850 MHz
30. Tuning a radio is example is:
(A) Mechanical resonance (B) Light wave resonance
(C) Electrical resonance (D) Physical resonance
31. At the open end of an organ pipe:
(A) Nodes are formed (B) Anti-nodes are formed
(C) Nodes or anti-nodes are formed (D) Neither node or anti-node
is formed
32. Period alternations of sound between maximum and minimum loudness are called:
(A) Interference (B) Resonance
(C) Doppler’s Effect (D) Beats
33. IF the organ pipe open at both ends the frequency of fundamental harmonic is:
(2times)
v v
f 1= f 1=
(A) 2ℓ (B) 4ℓ
4ℓ 2ℓ
f 1= f 1=
(C) v (D) v
34. If the string is made vibrate in n loops, then the wavelength of the stationary wave
will: (2times)
n 2
λ n= ℓ λ n= ℓ
(A) 2 (B) n
2n ℓ
λ n= λ n=
(C) ℓ (D) 2n
35. Laplace expression for the speed of sound in a gas is:

(A)
v=
√ P
ρ (B)
v=
p
ρ

(C)
v=
√ γP
ρ
36. Speed of sound at t 0C is given as:
(D)
v=
γp
ρ

(A)
v t =v 0 +0 .61 t (B)
v t =v 0 −0 . 61t

(C) t
v =v −61 t
0 (D)
v t =v 0 +61t
37. Which one is correct relation for one end closed pipe:
 (A)
λ n=2 ℓ/n (B)
λ n=4 ℓ/n

(C)
λ n=nℓ/ n (D)
λ n=nv /n

38. Distance between crest and trough is:

(A) λ (B) λ/2
(C) λ/4 (D) 2λ
39. The example of mechanical wave is:
(A) Water and air waves (B) Radio waves
(C) Infrared waves (D) Ultraviolet waves
40. Wavelength of the fundamental mode of vibrating of a closed end pipe is:
(A) 2ℓ (B) ℓ
(C) 4ℓ (D) 1/2ℓ
41. Sound waves can travel only through:
(A) Vacuum (B) Ether
(C) Material medium (D) Non metals
42. Newton’s formula for velocity of sound in gas/air is related as under:

(A) V =E / ρ
V =√E / ρ
(B)
V=
√ E
ρ
(C) (D) V = p / ρ
43. According to Newton’s sound travels in air under condition of:
(A) Adiabatic (B) Isothermal
(C) Isobaric (D) Isochoric
44. For standing wave in a stretched string if λ=ℓ (length of string) the number of loops
will be:
(A) 1 (B) 2
(C) 3 (D) 4
45. Two waves of same frequency and moving in the same direction produces:
(A) Interference (B) Diffraction
(C) Beats (D) Stationary
46. Two tuning forks of frequencies 240Hz and 243 Hz are sounded together, the
number of beats per second is:
(A) Zero (B) 4
(C) 3 (D) 2
47. With increase of temperature, speed of sound: (2times)
(A) Remain constant (B) Becomes zero
(C) Decreases (D) Increases
48. What is the value of constant β in the expression vt = vo (1 +βt):
(A) 273 (B) 1/273
(C) 0.61 (D) 1.42
49. The apparent change in the pitch of sound due to relative motion is called:
(A) Carnot theorem (B) Anti-node
(C) Doppler Effect (D) Beats
50. The portion of wave above mean level is called:
(A) Node (B) Anti-node
(C) Crest (D) Through
51. According to Newton’s formula the speed of sound in air at STP is:
(A) 332 ms-1 (B) 340 ms-1
(C) 350 ms -1
(D) 280 ms-1
52. Speed of sound in copper is:
(A) 38000 ms-1 (B) 3600 ms-1
(C) 3500 ms -1
(D) 3400 ms-1
53. Starts moving towards the earth show:
(A) Red shift (B) Blue shift
(C) Yellow shift (D) Green shift
54. The distance between two consecutive anti-nodes is:
λ
(A) λ (B) 4
λ
(C) 2 (D) 2 λ
55. The dimension of elastic modulus ‘ε’ is:
(A) ML-1T2 (B) ML-2T2
(C) MLT 2
(D) ML2T2
56. The distance between node and next antinode is:
(A) λ (B)2λ
λ λ
(C) 2 (D) 4
57. Sound waves in air are:
(A) Longitudinal waves (B) Transverse waves
(C) Matter waves (D) Electromagnetic waves
58. In stationary wave the point which always remain at rest are:
(A) Node (B) Anti-node
(C) Crest (D) Through
59. This correct relation is:
v
V=
(A) V = λT (B) T
λ
V=
(C) f (D) V =fλ
60. In a stationary wave, the velocity of the particle at the node is:
(A) Maximum (B) Minimum
(C) Zero (D) Constant
61. The speed of sound in air is 340 m/s. if the pressure of air is doubled then the
speed becomes:
(A) Double (B) Half
(C) Four time (D) Remain same
62. Transverse waves are distinguished form longitudinal waves by the property:
(A) Interference (B) Diffraction
(C) Reflection (D) Polarization
63. When the amplitude of a wave increases to doubled its energy:
(A) Remain the same (B) Increase by two times
(C) Increase by 4 times (D) Decrease to half
64. Velocity of sound in vacuum is:
(A) 332ms-1 (B) 320 ms-1
(C) Zero (D) 224 ms-1
65. Speed of sound is greatest in:
(A) Aluminum (B) Air
 (C) Iron (D) Water
66. Speed of sound in aluminum at 20oC is:’
(A) 3600 m/s (B) 5100 m/s
(C) 5130 m/s (D) 5500 m/s
67. If the tension of a stretched string is made four times then the velocity of wave:
(A) Remain same (B) Is haved
(C) Becomes twice (D) Becomes 4 times
68. When two identical waves superimposed, which can change:
(A) Wavelength (B) Frequency
(C) Velocity (D) Amplitude
69. The basic principle of beast is:
(A) Inference (B) Diffraction
(C) Reflection (D) Refraction
70. The distance covered by wave in 1-sec is:
(A) Wavelength (B) Wave number
(C) Frequency (D) Wave speed
71. The wavelength of fundamental mode of vibration of an open end pipe is:
(A) 4l (B) 2l
(C) l (D) ¼ l
72. Two tuning forks of frequency 260Hz and 256Hz are sounded together:
(A) 4 (B) 258
(C) 2 (D) 516
73. IF the pressure of a gas is doubled, then speed of sound is:
(A) Doubled (B) Becomes half
(C) Not affected (D) Increase by four time
74. The path difference for constructive interference should be:
λ 5λ
(A) 2 (B) 2
3λ
(C) λ (D) 2
75. Sound travels faster in:
(A) CO2 (B) H2
(C) O2 (D) He
76. Half wavelength corresponds to:
(A) 0o (B) 90o
(C) 180o (D) 360o
77. Longitudinal waves are also knows as:
(A) Stationary waves (B) Transverse waves
(C) Compressional (D) Electromagnetic waves
78. Tuning fork is a source of:
(A) Energy (B) Heat
(C) Light (D) Sound

OBJECTIVE ANSWERS
01 B 02 D 03 D 04 A 05 C
06 A 07 D 08 A 09 C 10 D
11 A 12 C 13 B 14 B 15 D
16 A 17 B 18 D 19 B 20 A
21 B 22 C 23 C 24 D 25 C
26 A 27 A 28 A 29 C 30 C
31 B 32 D 33 A 34 B 35 C
36 A 37 B 38 B 39 A 40 C
41 C 42 C 43 B 44 B 45 A
46 C 47 D 48 B 49 C 50 C
51 D 52 B 53 B 54 D 55 A
56 D 57 A 58 A 59 D 60 C
61 D 62 D 63 A 64 C 65 C
66 B 67 C 68 D 69 A 70 D
71 B 72 A 73 C 74 C 75 B
76 C 77 C 78 D