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Class 8 Science Chapter 10 Sound

Chapter 10 of Class 8 Science, titled "Sound," introduces students to the fascinating world of sound and its properties. The chapter explains how sound is produced, transmitted, and received, focusing on the role of vibrations in creating sound waves. Students will learn about the different mediums through which sound travels, such as solids, liquids, and gases, and how sound requires a medium to propagate. The concept of the speed of sound and factors that affect it, like temperature and medium, are also discussed. Furthermore, the chapter covers the structure of the human ear, how we perceive sound, and the importance of sound in communication. Additionally, students will explore topics like the range of hearing, the pitch and loudness of sound, and the effects of noise pollution. The quiz based on this chapter will test students' understanding of sound waves, the science behind how we hear, and the various applications and implications of sound in our daily lives. By the end of this chapter, students will have a clearer understanding of how sound influences the world around them.

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Category: Introduction to Sound

1. (A) The sound produced by a dog whistle cannot be heard by humans.
(R) The frequency of the sound produced by a dog whistle is above 20,000 Hz.

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Category: Role of sound in daily life

2. A sound wave has a frequency of 500 Hz and a wavelength of 0.68 meters. What is the speed of the sound wave?

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Category: Examples of sound perception

3. (A) A blindfolded person in the game hide and seek can identify the closest player based on the intensity of the sound produced by their footsteps.
(R) The intensity of sound decreases with distance from the source.

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Category: Basic questions about sound production and travel

4. Through which medium can sound NOT travel?

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Category: Sound is Produced by a Vibrating Body

5. (A) When a rubber band is plucked, it produces sound.
(R) Sound is produced due to the vibrations of the rubber band.

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Category: Definition of Vibration: To and fro motion of an object

6. When a rubber band is plucked, it vibrates and produces sound. What happens when the rubber band stops vibrating?

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Category: Experiments Demonstrating Vibrations

7. What happens when you hold a vibrating metal plate tightly after striking it with a stick? What does this demonstrate about sound production?

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Category: Striking a metal plate

8. Why does a metal dish produce sound when struck with a spoon?

9 / 100

Category: Plucking a rubber band

9. When a rubber band is plucked, what happens to it?

10 / 100

Category: Water vibrations in a dish

10. When a metal dish filled with water is struck at its edge, what happens to the water surface?

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Category: Musical Instruments and Vibrations

11. What part of the human body vibrates to produce sound when we speak?

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Category: String instruments (e.g., Veena, Sitar)

12. A stretched string of a musical instrument produces a sound wave with a frequency of 440 Hz. If the amplitude of the vibration is doubled, how does this affect the loudness of the sound perceived by the listener?

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Category: Membrane instruments (e.g., Tabla, Dholak)

13. Which of the following instruments produces sound by vibrating its membrane?

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Category: Percussion instruments (e.g., Ghatam, Manjira)

14. What would you observe if you strike a Manjira gently with a stick and immediately hold it tightly?

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Category: Sound Produced by Humans

15. Why do men, women, and children have different voices?

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Category: Voice Box (Larynx)

16. (A) The pitch of sound produced by humans is determined solely by the length of the vocal cords.
(R) Shorter vocal cords produce higher-pitched sounds because they vibrate at a higher frequency.

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Category: Location and function

17. Why do men generally have deeper voices compared to women?

18 / 100

Category: Role of vocal cords in sound production

18. How does the tightness of the vocal cords affect the quality of sound produced?

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Category: Variation in Voice

19. A person is asked to hum at a constant pitch for 10 seconds. During this time, what happens to the vocal cords and the air passing through them in the voice box?

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Category: Differences in men, women, and children’s voices

20. (A) The frequency of a child's voice is higher than that of an adult because their vocal cords are shorter.
(R) Shorter vocal cords vibrate at a higher frequency, producing higher-pitched sounds.

21 / 100

Category: Role of vocal cord length in pitch

21. (A) The pitch of a man's voice is lower than that of a woman because men have longer vocal cords.
(R) Longer vocal cords vibrate at a lower frequency, producing a lower pitch.

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Category: Sound Needs a Medium for Propagation

22. In an experiment, air is gradually removed

from a vessel containing a ringing bell. What happens to the loudness of the sound as more air is removed?

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Category: Experiments on Medium Requirement

23. (A) Sound cannot travel through a vacuum because there is no medium to carry the vibrations.
(R) A vacuum is defined as a space entirely devoid of matter, and sound requires a material medium for propagation.

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Category: Sound in air (Tumbler and cellphone experiment)

24. (A) Sound cannot be heard when all the air is removed from a vessel, creating a vacuum.
(R) Sound requires a medium to propagate, and a vacuum lacks such a medium.

25 / 100

Category: Sound in liquids (Water bucket and bell experiment)

25. (A) Sound can travel through liquids as demonstrated by the water bucket and bell experiment.
(R) In the water bucket and bell experiment, the sound produced by the bell is heard when the ear is placed on the water surface, indicating that sound waves propagate through the liquid medium.

26 / 100

Category: Sound in solids (Metal rod experiment)

26. (A) In a metal rod experiment, sound travels faster through the rod than through air.
(R) The speed of sound in solids is higher than in gases due to the closer arrangement of particles in solids.

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Category: Propagation of Sound in Different Media

27. A sound wave is traveling through three different media: air, water, and a metal rod. If the frequency of the sound wave remains constant, in which medium will the wavelength of the sound wave be the longest?

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Category: Gases: Air as a medium

28. Which of the following mediums allows sound to travel the fastest?

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Category: Gases: Air as a medium

29. (A) Sound cannot travel through a vacuum.
(R) Sound requires a medium, such as air, to propagate.

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Category: Liquids: Sound transmission underwater

30. A bell is shaken underwater to produce sound, and the sound is heard by placing an ear on the water surface. What does this experiment demonstrate?

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Category: Liquids: Sound transmission underwater

31. (A) Sound can travel through water because water molecules vibrate and transfer energy.
(R) The speed of sound in water is higher than in air due to the closer arrangement of water molecules.

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Category: Solids: Sound traveling through metal/wood

32. (A) Sound can travel through a metal rod.
(R) Sound requires a medium to propagate, and solids like metal provide a medium for sound to travel.

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Category: Solids: Sound traveling through metal/wood

33. (A) Sound can travel through solids like metal and wood.
(R) Solids provide a medium for sound waves to propagate due to their closely packed molecules.

34 / 100

Category: Concept of Vacuum

34. Why can’t sound travel through a vacuum?

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Category: Concept of Vacuum

35. In an experiment, a ringing cell phone is placed inside a dry tumbler, and air is sucked out. What observation supports the idea that sound needs a medium for propagation?

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Category: Sound cannot travel through a vacuum (e.g., space)

36. Why does the sound become fainter when air is sucked out of a tumbler during an experiment with a ringing cell phone?

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Category: Sound cannot travel through a vacuum (e.g., space)

37. Which of the following is an example of a medium that does not allow sound to travel?

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Category: We Hear Sound through Our Ears

38. What is the most likely consequence of inserting a sharp object into the ear?

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Category: We Hear Sound through Our Ears

39. (A) The eardrum vibrates when sound waves enter the ear.
(R) The eardrum sends vibrations to the inner ear, which then transmits the signal to the brain.

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Category: Structure of the Human Ear

40. (A) The eardrum vibrates when sound waves enter the ear.
(R) The eardrum sends vibrations to the inner ear, which then sends signals to the brain.

41 / 100

Category: Structure of the Human Ear

41. A student builds a tin-can model of the eardrum as described in Activity 10.10. If the friend speaks "Hurrey, Hurrey" louder, what would happen to the grains of cereal placed on the stretched rubber?

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Category: Outer ear: Funnel-like structure

42. (A) The outer ear has a funnel-like shape that helps in collecting sound waves.
(R) The funnel-like structure of the outer ear amplifies the sound waves before they reach the eardrum.

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Category: Outer ear: Funnel-like structure

43. (A) The outer ear is funnel-shaped to collect sound waves efficiently.
(R) The shape of the outer ear helps in directing sound waves towards the eardrum.

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Category: Middle ear: Eardrum (tympanic membrane)

44. A person speaks loudly near the open end of a tin-can model of the eardrum with grains placed on the stretched rubber membrane. What happens to the grains and why?

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Category: Middle ear: Eardrum (tympanic membrane)

45. What happens when sound waves reach the eardrum?

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Category: Inner ear: Nerve signals to the brain

46. What happens when sound waves reach the eardrum?

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Category: Inner ear: Nerve signals to the brain

47. Which of the following actions could potentially damage the eardrum?

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Category: Experiment on Eardrum Sensitivity

48. Why should sharp or hard objects never be inserted into the ear?

49 / 100

Category: Experiment on Eardrum Sensitivity

49. Why do grains placed on a stretched rubber sheet jump up and down when sound is produced near it?

50 / 100

Category: Model using a balloon stretched over a can

50. Consider a tin-can model of the eardrum with a stretched rubber balloon and grains of cereal on it. If the frequency of the sound produced by a friend increases, what happens to the movement of the grains?

51 / 100

Category: Model using a balloon stretched over a can

51. (A) The grains of dry cereal on the stretched rubber of the tin-can model jump up and down when sound is produced from the open end.
(R) The vibration of the rubber membrane due to sound waves causes the grains to move.

52 / 100

Category: Amplitude, Time Period, and Frequency of a Vibration

52. If the amplitude of a sound wave is tripled, by what factor does the loudness increase?

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Category: Amplitude, Time Period, and Frequency of a Vibration

53. What is the time period of a vibration if its frequency is 100 Hz?

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Category: Loudness and Pitch

54. Which of the following sounds would have the highest pitch?

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Category: Loudness and Pitch

55. (A) The loudness of a sound produced by a vibrating object is directly proportional to the amplitude of vibration.
(R) The pitch of a sound is determined by its frequency, while loudness is determined by the square of the amplitude of vibration.

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Category: Amplitude: Height of vibration affecting loudness

56. A vibrating object produces sound with an amplitude of 2 cm. If the amplitude is doubled, by what factor does the loudness increase?

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Category: Amplitude: Height of vibration affecting loudness

57. What is the time period of a vibration if its frequency is 20 Hz?

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Category: Time Period: Time taken for one complete vibration

58. A pendulum completes 60 oscillations in 15 seconds. What is the time period and frequency of the pendulum?

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Category: Time Period: Time taken for one complete vibration

59. Time taken by an object to complete one oscillation is called __________.

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Category: Frequency: Number of vibrations per second (Hertz, Hz)

60. Which of the following frequencies is audible to a human ear?

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Category: Frequency: Number of vibrations per second (Hertz, Hz)

61. Two sounds are produced with frequencies of 200 Hz and 400 Hz respectively. Which sound will have a higher pitch, and how many times higher is its frequency compared to the other?

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Category: Effect of Amplitude on Loudness

62. A sound wave has an amplitude of 2 units. If the amplitude is increased to 6 units, how many times louder will the sound be perceived?

63 / 100

Category: Effect of Amplitude on Loudness

63. (A) The loudness of sound increases when the amplitude of vibration increases.
(R) Loudness is directly proportional to the square of the amplitude of vibration.

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Category: Larger amplitude = Louder sound

64. Two sounds are produced with frequencies of 200 Hz and 400 Hz respectively. Which statement correctly describes the pitch of these sounds?

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Category: Larger amplitude = Louder sound

65. A sound wave has an amplitude of 2 units and a frequency of 50 Hz. If the amplitude is increased to 4 units while keeping the frequency constant, how does the loudness of the sound change?

66 / 100

Category: Measurement in decibels (dB)

66. (A) The loudness of sound increases when the amplitude of vibration increases.
(R) Loudness of sound is proportional to the square of the amplitude of vibration.

67 / 100

Category: Measurement in decibels (dB)

67. Which of the following sounds has the highest decibel level?

68 / 100

Category: Effect of Frequency on Pitch

68. Consider two sounds: one produced by a drum and another by a whistle. Which of the following statements about their frequencies and pitches is correct?

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Category: Effect of Frequency on Pitch

69. A drum produces a sound with a frequency of 50 Hz, while a whistle produces a sound with a frequency of 1000 Hz. Which statement correctly describes the pitch of these sounds?

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Category: High frequency → Shrill sound (e.g., bird chirp)

70. (A) A bird chirp has a higher pitch than a lion\'s roar because it has a higher frequency.
(R) The pitch of a sound is determined by its frequency.

71 / 100

Category: High frequency → Shrill sound (e.g., bird chirp)

71. A bird produces a sound with a frequency of 4000 Hz. What can be inferred about the pitch of this sound compared to a lion's roar with a frequency of 100 Hz?

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Category: Low frequency → Deep sound (e.g., lion’s roar)

72. A sound wave has a frequency of 20 Hz. What can be inferred about its pitch?

73 / 100

Category: Low frequency → Deep sound (e.g., lion’s roar)

73. A tuning fork vibrates 300 times in 5 seconds. If the amplitude of vibration is doubled, how will the loudness of the sound produced change?

74 / 100

Category: Audible and Inaudible Sounds

74. What is the range of audible frequencies for the human ear?

75 / 100

Category: Audible and Inaudible Sounds

75. A medical ultrasound device operates at a frequency of $25,000 Hz$. Which of the following statements is true regarding the sound produced by this device?

76 / 100

Category: Human Hearing Range

76. A sound wave has a frequency of $25 \text{ kHz}$. Which of the following statements is true regarding the audibility of this sound?

77 / 100

Category: Noise and Music

77. Which of the following health problems can be caused by noise pollution?

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Category: Definition of Noise and Music

78. Which of the following sounds is an example of noise?

79 / 100

Category: Noise: Unpleasant, irregular sounds

79. (A) Music cannot cause noise pollution because it is always pleasant to the ear.
(R) Noise pollution is caused only by sounds that are unpleasant and irregular.

80 / 100

Category: Music: Pleasant, rhythmic sounds

80. (A) The sound produced by a musical instrument is always pleasant to the ear, regardless of its amplitude.
(R) The pleasantness of a musical sound depends on the frequency of vibrations and not on the amplitude.

81 / 100

Category: Traffic sounds, construction, loudspeakers

81. In a classroom, if all students speak together, the sound produced is considered noise. Which of the following scenarios would also be classified as noise?

82 / 100

Category: Harmonium, flute, veena

82. When air is pumped into a harmonium, which part of the instrument primarily vibrates to produce musical sound?

83 / 100

Category: Noise Pollution

83. Which of the following is a measure to control noise pollution in residential areas?

84 / 100

Category: Sources of Noise Pollution

84. (A) Planting trees along roads and around buildings can significantly reduce the harmful effects of noise pollution in residential areas.
(R) Trees act as natural sound barriers by absorbing and deflecting sound waves, thus reducing the intensity of noise reaching the residents.

85 / 100

Category: Vehicles, factory machines, construction work

85. A construction site is located near a residential area. The sound level at the boundary of the residential area is measured to be 85 dB. If the construction site is moved 100 meters away from the residential area, and assuming the sound intensity follows the inverse square law, what will be the new sound level at the residential boundary?

86 / 100

Category: Home appliances (TV, loudspeakers)

86. A desert cooler and an air conditioner are both running in a home. The cooler produces 65 dB of noise, and the air conditioner produces 68 dB. What is the combined noise level?

87 / 100

Category: Effects of Noise Pollution

87. What is an effective measure to reduce noise pollution in a residential area?

88 / 100

Category: Health issues: Stress, anxiety, high blood pressure, hearing impairment

88. (A) Noise pollution can cause hearing impairment in individuals.
(R) Continuous exposure to loud sounds can damage the auditory system.

89 / 100

Category: Measures to Control Noise Pollution

89. (A) Planting trees along roads and around buildings is an effective measure to reduce noise pollution in residential areas.
(R) Trees act as natural sound barriers that absorb and scatter sound waves, thereby reducing the noise levels reaching the residents.

90 / 100

Category: Use of silencers in vehicles

90. What is one effective measure to reduce noise pollution in residential areas?

91 / 100

Category: Plantation of trees

91. (A) Planting trees along roads and around buildings is an effective method to reduce noise pollution in residential areas.
(R) Trees act as natural sound barriers by absorbing, deflecting, and diffracting sound waves, thereby reducing the intensity of noise reaching the residents.

92 / 100

Category: Keeping industries away from residential areas

92. A new industrial zone is being planned near a residential area. The noise level at the boundary of the residential area is currently 50 dB. If the industrial zone is expected to produce an additional 40 dB of noise, what will be the combined noise level at the boundary if both sources are active?

93 / 100

Category: Hearing Impairment

93. Which of the following can help children with hearing impairment communicate effectively?

94 / 100

Category: Causes of Hearing Impairment

94. A child accidentally inserts a sharp object into their ear, leading to a damaged eardrum. What is the most likely long-term consequence of this action?

95 / 100

Category: Congenital deafness

95. (A) Total hearing impairment is usually present from birth.
(R) Congenital deafness is a common cause of total hearing impairment.

96 / 100

Category: Damage due to disease or injury

96. (A) Exposure to excessive noise pollution can lead to permanent hearing impairment.
(R) Continuous loud sounds can damage the eardrum, causing hearing loss.

97 / 100

Category: Technological Support

97. Which of the following technological devices is commonly used to assist individuals with hearing impairment?

98 / 100

Category: Hearing aids, sign language

98. A hearing-impaired individual uses a cochlear implant and also relies on sign language for communication. How does this combination contribute to their quality of life?

99 / 100

Category: Social Awareness

99. (A) Children with hearing impairment can lead normal lives with the help of technological devices and societal support.
(R) Technological devices for the hearing-impaired have significantly improved their quality of life, and society plays a crucial role in creating a supportive environment.

100 / 100

Category: Helping hearing-impaired individuals integrate into society

100. What role do technological devices play in the lives of hearing-impaired individuals?

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