Sound Worksheet-8

Sound Worksheet-8

61. Define the terms 'frequency', 'wavelength' and 'velocity' of a sound wave. What is the relation between them?

62. A body vibrating with a time-period of (1/256) s produces a sound wave which travels in air with a velocity of 350 m/s. Calculate the wavelength.

63. What are longitudinal waves and transverse waves? Explain with the help of labelled diagrams.

Give two examples each of longitudinal waves and transverse waves.

64. Explain the terms 'compressions' and 'rarefactions' of a wave. What type of waves consist of   compressions and rarefactions?

65. A worker lives at a distance of 1.32 km from the factory. If the speed of sound in air be 330 m/s, how much time will the sound of factory siren take to reach the worker?

66. Explain the terms 'crests' and 'troughs' of a wave? What type of waves consist of crests and troughs?

67. The flash of a gun is seen by a man 3 seconds before the sound is heard. Calculate the distance of the gun from the man (Speed of sound in air is 332 m/s).

68. When we put our ear to a railway line, we can hear the sound of an approaching train even when the train is far off but its sound cannot be heard through the air. Why?

69. How could you convince a small child that when you speak, it is not necessary for air to travel from your mouth to the ear of a listener?

70. Draw the sketches of two waves A and B such that wave A has twice the wavelength and half the amplitude of wave B.

71. A device called oscillator is used to send waves along a stretched string. The string is 20 cm long, and four complete waves fit along its length when the oscillator vibrates 30 times per second. For the waves on the string :

Find wavelength, frequency and speed?   

72. Through which of the following materials can sound travel?

Wood, air, water, steam, ice, hydrogen, steel, diamond.

73. A sound producing body is at considerable distance from a man. There can be four different media W, X, Y and Z between the sound producing body and the man. The medium X brings the sound to man most quickly whereas medium Z takes the maximum time. The time taken by medium W in bringing sound to man is less than that of X but more than that of Z. The medium Y, however, fails to bring the sound from the sound producing body to the man.

Say about the mediums,

(a) Which has no fixed shape and no fixed volume?

(b) Which has a fixed volume but no fixed shape?

(c) Which has the same composition as that on the moon?

(d) Which has a fixed shape and a fixed volume?

74. The longitudinal waves travel in a coiled spring at a rate of 4 m/s. The distance between two consecutive compressions is 20 cm. Find :

Wavelength and frequency of the wave

75. Which property of sound leads of the formation of echoes?

76. What name is given to the repetition of sound caused by the reflection of sound waves?

77. What name is given to the persistence of sound in a big hall or auditorium?

78. Name three devices which work on the reflection of sound.

79. What is the other name of a loud-hailer?

80. Name the three characteristics of sound.

Answer:

61. –

62. 1.36 m

63. –

64. –

65.  4 s

66. –

67. 996 m

68. –

69. –
70. 

71. 5 cm (or 0.05m) , 120 Hz , 6 m/s

72. Sound can travel through all the given materials

73. Sound is a mechanical wave and needs a material medium like air, water, steel etc. for its propagation. Sound travels fastest in solids then liquid and then gases. Here gases have no fixed volume and shape, liquid have fixed volume but no fixed shape and solids have fixed shape and volume. Sound cannot travel through vaccum.

(a)  Z  (b)  W  (c)  Y  (d)  X

74. (i) 20 cm  (ii) 20 Hz.

75. Reflection of sound

76. Echo

77. Reverberation

78. Megaphone, Stethoscope, sound board

79. Megaphone

80. –