# CBSE Class 8 Science Sound Assignment

Read and download free pdf of CBSE Class 8 Science Sound Assignment. Get printable school Assignments for Class 8 Science. Class 8 students should practise questions and answers given here for Chapter 13 Sound Science in Class 8 which will help them to strengthen their understanding of all important topics. Students should also download free pdf of Printable Worksheets for Class 8 Science prepared as per the latest books and syllabus issued by NCERT, CBSE, KVS and do problems daily to score better marks in tests and examinations

## Assignment for Class 8 Science Chapter 13 Sound

Class 8 Science students should refer to the following printable assignment in Pdf for Chapter 13 Sound in Class 8. This test paper with questions and answers for Class 8 Science will be very useful for exams and help you to score good marks

### Chapter 13 Sound Class 8 Science Assignment

Question 1: How does the sound produced by a vibrating object in a medium reach your ear?

Answer- When a disturbance is created on an object, it starts vibrating and sets the particles of the medium to vibrate. These vibrating particles take the sound from object to our ear through the medium.

Question 2: Explain how sound is produced by your school bell.
Answer- When the school bell is struck with a hammer, it starts vibrating and as a result of these vibrations,sound waves are produced.

Question 3: Why are sound waves called mechanical waves?
Answer- Because sound waves require a medium to propagate to interact with the particles present in it.

Question 4: Suppose you and your friend are on the moon. Will you be able to hear any sound produced by your friend?
Answer- No, we will not be able to hear the sound because sound requires a medium for its propagation. On the moon there is no atmosphere, i.e., there is vacuum.

Question 5: Which wave property determines (a) loudness, (b) pitch?
Answer- (a) Loudness is determined by the amplitude of the sound wave which in turn depends on the force with which the object is made to vibrate.
(b) Pitch of a sound is determined by its frequency.

Question 6: Guess which sound has a higher pitch: guitar or car horn?

Question 7: What are wavelength, frequency, time period and amplitude of a sound wave?
Answer- a) Wavelength(λ) : The distance between two consecutive compressions (C) or two consecutive rarefactions (R) is called the wavelength, unit-metre.
(b) Frequency : The number of oscillations per unit time is called frequency, unit-Hz.
(c) Time period : The time taken by two consecutive compressions or rarefactions to cross a fixed point is called the time period.
(d) Amplitude : The magnitude of the maximum disturbance in the medium on either side of the mean value is called the amplitude of the wave.

Question 8: How are the wavelength and frequency of a sound wave related to its speed?
Answer- Speed = Wavelength x Frequency.

Question 9: Calculate the wavelength of a sound wave whose frequency is 220 Hz and speed is 440 m/s in a given medium.
Answer- Frequency = f = 220 Hz
Speed of sound = v = 440 m/s
Wavelength = λ = v/f = 440/220 = 2 m.

Question 10: A person is listening to a tone of 500 Hz sitting at a distance of 450 m from the source of the sound. What is the time interval between successive compressions from the source?
Answer- Frequency = f = 500 Hz
Time between successive compressions = Time period of sound wave = T = 1/f = 1/500 = 0.002 sec.

Question 11: Distinguish between loudness and intensity of sound.
Loudness of sound                                                         Intensity of sound
1. Loudness refers to how loud or soft a sound seems to a listener.    1. Intensity is defined as the power carried by sound waves per unit area.
2. Loudness of sound is determined of amplitude.                             2. Intensity of the sound wave is determined by frequency of sound waves.
3. The unit of loudness is the decibel (dB).                                       3. The unit of intensity of sound is watt per square meter (W/m2).

Question 12: In which of the three media, air, water or iron, does sound travel the fastest at a particular temperature?

Question 13: Why are the ceilings of concert halls curved?
Answer- Ceilings of concert halls are curved to uniformly spread sound in all directions after reflecting from the walls.

Question 14: What is the audible range of the average human ear?
Answer- 20 Hz to 20,000 Hz.

Question 15: What is the range of frequencies associated with (a) Infrasound? (b) Ultrasound?
Answer- (a) Infrasound: Less than 20 Hz ; (b) Ultrasound: More than 20000 Hz

More Question

I. Fill in the blanks.

1. To and fro or back and forth motion of an object is called ___________.

2. In humans the sound is produced by the ________ or the ___________.

3. ________ are stretched across the voice box or larynx.

4. The vocal cords in men are about ______ mm long.

5. Noise becomes physically painful at _____ dB.

6. Frequency determines the ________ of a sound.

7. ________ on the roadside and elsewhere can reduce noise pollution.

8. _________ and _______ are two important properties of sound.

9. ________ senses the vibrations of sound.

II. Name the following

1. An instrument used for investigating and tracking many medical problems.

2. Name the major causes of noise pollution.

3. Name the sources in home which may lead to noise.

4. Give examples of objects which produce sounds of low frequency or low pitched.

5. Give examples of objects which produce sound of high frequency or high pitched.

Some Natural Phenomena

Q1. What type of electric charge is acquired by a rubber balloon when rubbed with a woolen cloth?

Q2. A positively charged object repels another charged object kept close to it. What is the nature of charge on the other object?

Q3. A glass rod is rubbed with a silk cloth & a rubber balloon is rubbed with a woolen cloth.

a) Which two objects acquire negative charge?

b) Which two objects acquire positive charge?

Q4. Explain why, a glass rod can be charged by rubbing when held by hand but an iron rod cannot be charged by rubbing, if held by hand?

Q5. Consider three charged bodies P, Q & R. If P & Q repel each other & P attracts R. What is the nature of force between Q & R?

Q6. Name the device used to detect electric charge on a body. Draw its labeled diagram.

Q7. What will you observe when the metal cap of an electroscope is touched with a glass rod which has been rubbed with silk cloth? Give reason for your answer.

Q8. What are the uses of an electroscope? (3 points)

Q9. Why do the leaves of a gold leaf electroscope diverge when a charged body is brought in contact with its disc?

Q10. Do the leaves of an electroscope always diverge to the same extent when a charged body is brought in contact with its disc?

Q11. What will you observe when the metal cap of an electroscope is touched with:

a) A positively charged object?

b) A negatively charged object?

Question 1: What is sound and how is it produced?

Answer- Sound is a form of energy and it is produced due to vibrations of different types of objects.

Question 2: Describe with the help of a diagram, how compressions and rarefactions are produced in the air near a source of sound.
Answer- (1) When a vibrating object moves forward, it pushes the air in front of it and compresses the air creating a region of high pressure called compression (C).
(2) It starts moving away from the surface of the vibrating object.
(3) As this occurs the surface moves backward creating a region of low pressure called rarefaction (R) Question 3: Cite an experiment to show that sound needs a material medium for its propagation.
Answer- Take an electric bell and an air tight glass bell jar. The electric bell is suspended inside an air tight glass jar which is connected to a vacuum pump. Working:
1. When we press the switch, we will be able to hear the bell
2. When the air in the jar is pumped out gradually, the sound becomes feeble although the same amount of current is flowing through the bell.
3. When the air is removed completely, are will not be able to hear the sound of the bell.
Conclusion: This experiment shows that sound requires a medium for its propagation.

Question 4: Why sound wave is called a longitudinal wave?
Answer- A sound wave is called a longitudinal wave as it travels in a medium by the vibration of particles in a direction which is parallel to the direction of propagation of the sound wave.

Question 5: Which characteristics of the sound help you to identify your friend by his voice while sitting with others in a dark room?
Answer- The quality (or timbre), pitch and loudness of sound.

Question 6: Flash and thunder are produced simultaneously. But thunder is heard a few seconds after the flash is seen, why?
Answer- The speed of light is much higher than speed of sound. Due to this reason, the thunder takes more time to reach the Earth as compared to the light. Hence, lightning is seen before whenever we hear the thunder

Question 9: The frequency of a source of sound is 100 Hz. How many times does it vibrate in a minute?
Number of vibrations in 1 second = 100
Number of vibrations in 60 second = 100 x 60
Number of vibrations in 1 minute = 6000.

Question 10: Does sound follow the same laws of reflection as light does? Explain.
Answer- Yes, sound follows the same laws of reflection as light does because,
(1) Angle of incidence of sound is always equal to angle of reflection of sound waves.
(2) The direction in which sound is incident, the direction in which it is reflected and normal all lie in the same plane.

Question 11: When a sound is reflected from a distant object, an echo is produced. Let the distance between the reflecting surface and the source of sound production remains the same. Do you hear echo sound on a hotter day?
Answer- An echo is heard when time interval between the reflected sound and the original sound is at least 0.1 second. As the temperature increases, the speed of sound in a medium also increases. On a hotter day, the time interval between the reflected and original sound will decrease and an echo is audible only if the time interval between the reflected sound and the original sound is greater than 0.1 s.

Question 12: Give two practical applications of reflection of sound waves.
Answer- (i) Reflection of sound is used to measure the speed and distance of underwater objects. This method is called SONAR.
(ii) Working of a stethoscope - the sound of patient’s heartbeat reaches the doctor’s ear through multiple reflections of sound.

Question 15: What is reverberation? How can it be reduced?
Answer- The continuous multiple reflections of sound in a big enclosed space is reverberation. It can be reduced by covering walls and ceiling of enclosed space with the help of sound absorbing materials such as loose woollens, fibre boards.

Question 16: What is loudness of sound? What factors does it depend on?
Answer- Loudness refers to how loud or soft a sound seems to a listener. Loudness of sound is determined of amplitude. The unit of intensity is the decibel (dB).

Question 17: Explain how bats use ultrasound to catch prey.
Answer- The ultrasonic waves emitted by the bat are reflected from the prey (e.g., an insect) and are detected by its ears . The nature of reflected waves tells the bat about the location and the nature of its prey.

Question 18: How is ultrasound used for cleaning?
Answer- Objects that need to be cleansed are put in a cleaning solution and ultrasonic sound waves are passed through the solution. The high frequency of ultrasound waves helps in detaching the dirt from the objects.

Question 19: Explain the working and application of a SONAR.
Answer- SONAR;(-Sound Navigation and Ranging).It consists of a transmitter and a detector and is installed in a boat or a ship as shown in figure: More Question

Q.1 How does a sound making object differ from one that is silent?

Q.2 How does sound from a sound producing body travel through air to reach our ears?

Q.3 Why are the voices of men, Women and children different?

Q.4 Why a sound cannot be heard on the moon?

Q.5 How do astronauts talk to one another on the surface of moon and Why?

Q.6 If you want to hear a train approaching from far away, why is it more convenient to put the ear to the track?

Q.7 State one observation from everyday life which shows that sound travels much more slowly than light?

Q.8 What is the scientific name for the following?

The number of vibrations made per second.

Q.9 Why do we not hear the screams of a bat?

Q.10 Which of the following frequency of sound can be heard by a dog but not by a man? {a} 50,000 hertz {b} 15,000 hertz

Q.11 Explain how, noise pollution {or excessive loud noise} is harmful to human beings.

Q.12 State the various measures which can be taken to control {or reduce} noise pollution in our surroundings.

Q.13 Give two causes of noise pollution from the homes.

Q.14 Sound of different pitch can be produced using a flute. Explain, how?

1.Loudness of sound is measured on a scale called:
(A) Vernier scale.
(B) Decibel scale.
(C) Meter scale.
(D) Screw gauge.

2.What is velocity of sound in water?

(A) 1500 m/s.
(B) 330 m/s.
(C) 200 m/s.
(D) 330 m/s.

3.For an echo to be heard, the minimum distance between the source and reflecting surface must be ………

(A) 17 m.
(B) 17 cm.
(C) 10 m.
(D) 10 cm.

4.A pendulum vibrates 50 oscillations in 5 seconds. Calculate its frequency?

(A) 10 Hz.
(B) 20 Hz.
(C) 50 Hz.
(D) None.

5.What is sound?

6.How is a sound produced?

7.How is sound propagates?

8.What is the amplitude of the wave?

9.What is the use of reflection of sound?

10.On what factor does loudness of sound depend?

11.Where will the sound travel faster, in wood or water?

12.Define frequency of sound.

13.Define the term pitch.

14.Define the term echo.

15.What is the audible range of human ear?

16.What is the full form of SONAR?

17.Name the section of throat in which human voice is produced.

18.What is ultrasound?

19.Write one difference between musical sound and noise.

20.Name the two animals that use echo-location to guide them.

21.Sound can travel through:
(A) Gases only.
(B) Solids only.
(C) Liquids only.
(D) Solid, liquids and gases.

22.What is velocity of sound in air?
(A) 300 m/s.
(B) 330 m/s.
(C) 280 m/s.
(D) 200 m/s.

23.The number of oscillations per second is called:
(A) Time period.
(B) Amplitude.
(C) Frequency.
(D) None.

24.On what factor does loudness of sound depend?
(A) Pitch.
(B) Frequency.
(C) Time period.
(D) Amplitude.

25.Sound is produced when objects:
(A) Rotate.
(B) Vibrate.
(C) Circulate.
(D) None.

26.Name the section of throat in which the human voice is produced.
(A) Wind pipe.
(B) Larynx.
(C) Vocal cord.
(D) None.

27.The audible range of frequency for human ear is:
(A) Less than 20 Hz.
(B) 20 to 20,000 Hz.
(C) More than 20,000 Hz.
(D) None.

28.Bats and dolphins can produce and hear sounds with a frequency of:
(A) 12,000 Hz.
(B) 1,20,000 Hz.
(C) 1200 Hz.
(D) 120 Hz.

29.Shrillness of a sound is determined by the……………… of vibration.
(A) Frequency.
(B) Amplitude.
(C) Time period.
(D) Loudness.

30.Vibrating part of the tabla is:
(A) Stretched membrane.
(B) Stretched string.
(C) Air column.
(D) Water column.

31.Frequency is measured in:
(A) Hertz.
(B) Second.
(C) Per second.
(D) (a) & (c).

32.Vibrating part of the sitar is:
(A) Stretched membrane.
(B) Stretched string.
(C) Air column.
(D) Water column.

33.Vibrating part of the flute is:
(A) Stretched membrane.
(B) Stretched string.
(C) Air column.
(D) Water column.

34.Vibrating part of the Jaltarang is:
(A) Stretched membrane.
(B) Stretched string.
(C) Air column.
(D) Water column.

35.Waves of frequency greater than 20,000 Hz are called:
(A) Panasonic.
(B) Ultrasonic.
(C) Sonic.
(D) None.

36.In which medium speed of sound is maximum:
(A) Solid.
(B) Liquid.
(C) Air.
(D) Vacuum.

37.A small instrument having two prongs is called:
(A) Tuning fork.
(B) Larynx.
(C) (a) & (b).
(D) None.

38.A sensation depending upon frequency is known as:
(A) Loudness.
(B) Pitch.
(C) Noise.
(D) Shrill.

39.Which is not characteristic of sound:
(A) Pitch.
(B) Noise.
(C) Loudness.
(D) Shrill.

40.Reflected sound is called:
(A) Music.
(B) Noise.
(C) Echo.
(D) None.

41.To and fro motion of an object about its mean position is called:
(A) Oscillatory motion.
(B) Linear motion.
(C) Circular motion.
(D) None.

42.The loudness of sound is proportional to the:
(A) Amplitude.
(B) Square of amplitude.
(C) Frequency.
(D) Square of frequency.

43.If the amplitude of sound become twice then loudness increases by factor:
(A) 2.
(B) 4.
(C) 8.
(D) It will not increase.

44.The voice of a woman has a higher…………… and ………….. than that of a man.
(A) Loudness and amplitude.
(B) Loudness and pitch.
(C) Frequency and pitch.
(D) Frequency and amplitude.

45.High pitch sound has …………… frequency.
(A) high
(B) low
(C) negative
(D) None.

46.Sounds of frequencies less than about 20 vibrations per second called:
(A) Audible.
(B) Ultrasonic.
(C) Inaudible.
(D) None.

47.Presence of excessive or unwanted sounds in the environment is called:
(A) Music.
(B) Noise.
(C) Noise pollution.
(D) None.

48.Which of the following voices is likely to have minimum frequency?
(A) Baby girl.
(B) Baby boy.
(C) A man.
(D) A woman.

49.The maximum distance through which a vibrating body is displaced from its mean position is called:
(A) Frequency.
(B) Amplitude.
(C) Pitch.
(D) None.

50.In human beings, voice is produced by the vibration of their:
(A) Wind pipe.
(B) Vocal chord.
(C) Larynx.
(D) None.

51.If an object makes 10 oscillations in 1 second, then what is its frequency?
(A) 1 Hz.
(B) 10 Hz.
(C) 5 Hz.
(D) 8 Hz.

52.If an object makes 10 oscillations in 2 seconds, then what is its frequency?
(A) 1 Hz.
(B) 10 Hz.
(C) 5 Hz.
(D) 8 Hz.

53.If an object makes 10 oscillations in 1 second, then what is its time period?
(A) 1 sec.
(B) 0.1 sec.
(C) 0.01 sec.
(D) 10 sec.

54.Time taken by an object to complete one oscillation is called:
(A) Frequency.
(B) Pitch.
(C) Amplitude.
(D) Time period.

55.Vibration below ……………. is called infra sound.
(A) 10 dB.
(B) 0dB.
(C) 90 dB.
(D) None.

<2M>

56.What is ultrasound? State one characteristic of ultrasound which makes it useful in the process of echo-location.

57.What is timber?

58.In cinema halls and auditoria, the walls, floor and ceilings are covered by sound absorbing materials, why?

59.Write the following frequency in their increasing order: (i) Voice of a child, (ii) Voice of a man, (iii) Voice of a
woman.

60.A pendulum produces 20 oscillations in 5 second. Calculate its time period?

<3M>

61.Give reason:
(i) During a thunderstorm, we first see the lightning and then hear the thunder.
(ii) We do not hear the supersonic jet approaching, but hear a sudden boom after it has passed away

62.How is the human voice produced?

63.Explain how sound is produced by each of the following types of musical instruments.
(i) Wind instruments. (ii) String instruments. (iii) Percussion instruments.

64.How would you describe the sound produced if
1. A large number of vibrations are produced per second.
2. The amplitude is small.
3. Vibrations are produced at irregular intervals.

65.Sound produced by a mosquito is quite different from the roar of a lion. Explain.

66.Write differences between musical sound and noise.

<5M>

67.What do you understand by term noise pollution?Write some harmful effects of noise pollution.

68.Differentiate between loudness and pitch.

69.What do you understand by term noise pollution? Suggest some ways of minimizing noise pollution.

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### CBSE Class 8 Science Chapter 13 Sound Assignment

We hope you liked the above assignment for Chapter 13 Sound which has been designed as per the latest syllabus for Class 8 Science released by CBSE. Students of Class 8 should download and practice the above Assignments for Class 8 Science regularly. We have provided all types of questions like MCQs, short answer questions, objective questions and long answer questions in the Class 8 Science practice sheet in Pdf. All questions have been designed for Science by looking into the pattern of problems asked in previous year examinations.

#### Assignment for Science CBSE Class 8 Chapter 13 Sound

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#### Chapter 13 Sound Assignment Science CBSE Class 8

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#### Chapter 13 Sound Assignment CBSE Class 8 Science

Regular assignment practice helps to get a more comprehensive understanding of Chapter 13 Sound concepts. Assignments play a crucial role in understanding Chapter 13 Sound in CBSE Class 8. Students can download all the assignments of the same chapter in Class 8 Science in Pdf format. You can print them or read them online on your computer or mobile.

#### CBSE Science Class 8 Chapter 13 Sound Assignment

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