Sound Worksheet-7

Sound Worksheet-7

41. (a) Distinguish between longitudinal and transverse waves.

(b) Are sound waves longitudinal or transverse?

42. A cricket ball is seen to hit the bat first and the sound of hitting is heard a little later. Why?

43. Explain why, the flash of lightning reaches us first and the sound of thunder is heard a little later.

44. Explain why, the flash of a gun shot reaches us before the sound of the gun shot.

45. Which of the following terms apply to sound waves in air and which to water waves?

Transverse, Rarefaction, Trough, Crest, Compression, Longitudinal

46. Calculate the speed of a sound wave whose frequency is 2 kHz and wavelength 65 cm.

47. If a ringing bicycle bell is held tightly by hand, it stops producing sound. Why?

48. Give reason for the following :

In most of the cases, we cannot see the vibrations of a sound producing object with our eyes.

49. Describe a simple experiment to show that the prongs of a sound producing tuning fork are vibrating.

50. When we open a gas tap for a few seconds, the sound of escaping gas is heard first but the smell of gas comes later. Why?

51. A sound signal of 128 vibrations per second has a wavelength of 2.7 m. Calculate the speed with which the wave travels.

52. A wave is moving in air with a velocity of 340 m/s. Calculate the wavelength if its frequency is 512 vibrations/sec.

53. Define the 'frequency' and 'time-period' of a wave. What is the relation between the two?

54. Explain why, a ringing bell suspended in a vacuum chamber cannot be heard outside.

55. The frequency of the sound emitted by the loudspeaker is 1020 Hz. Calculate the wavelength of the sound wave in air in cm where its velocity is 340 m/s.

56. What is the difference between a compression and a rarefaction in a sound wave? Illustrate your answer with a sketch.

57.  Describe an experiment to show that sound cannot pass through vacuum.

58. How is sound produced? Explain with the help of an example.

How does sound from a sound producing body travel through air to reach our ears? Illustrate your answer with the help of a labeled diagram.

59. An electric bell is suspended by thin wires in a glass vessel and set ringing. Describe and explain what happens if the air is gradually pumped out of the glass vessel.

60. Why cannot a sound be heard on the moon? How do astronauts talk to one another on the surface of moon?

Answer:

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42. Light waves travel faster than sound waves

43. Light waves travel faster than sound waves

44. Light waves travel faster than sound waves

45. Sound waves : Longitudinal, Compression Rarefaction;

water waves: Transverse, Crest, Trough

46. 1300 m/s

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51. 345.6 m/s

52. 0.66 m

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54. Sound is a mechanical wave and needs a material medium like air, water, steel etc. for its propagation. It cannot travel through vacuum,

55. 33.3 cm

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