Class–VIII (CHAPTER-13) SOUND Question
1. Choose the correct answer.
Sound can travel through
(a) gases only (b) solids only
(b) liquids only (d) solids, liquids and gases.
2. Which of the following voices is likely to have minimum frequency?
(a) Baby girl (b) Baby boy
(b) A man (d) A woman
3. In the following statements, tick ‘T’ against those which are true, and ‘F’ against those which are false.
(a) Sound cannot travel in vacuum. (T / F) (b) The number of oscillations per second of a vibrating object is called its time period. (T / F)
(c) If the amplitude of vibration is large, sound is feeble. (T / F) (d) For human ears, the audible range is 20 Hz to 20,000 Hz.
(T / F) (e) The lower the frequency of vibration, the higher is the pitch.
(T / F) (f) Unwanted or unpleasant sound is termed as music. (T / F) (g) Noise pollution may cause partial hearing impairment. (T / F)
4. Fill in the blanks with suitable words.
(a) Time taken by an object to complete one oscillation is called
(b) Loudness is etermined by the of vibration. (c) The unit of frequency is .
(d) Unwanted sound is called .
(e) Shrillness of a sound is determined by the of vibration.
5. A pendulum oscillates 40 times in 4 seconds. Find its time period and frequency.
6. The sound from a mosquito is produced when it vibrates its wings at an average rate of 500 vibrations per second. What is the time period of the vibration?
7. Identify the part which vibrates to produce sound in the following instruments.
(a) Dholak (b) Sitar (c) Flute
8. What is the difference between noise and music? Can music become noise sometimes?
9. List sources of noise pollution in your surroundings.
10. Explain in what way noise pollution is harmful to humans.
11. Your parents are going to buy a house. They have been offered one on the roadside and another three lanes away from the roadside. Which house would you suggest your parents should buy? Explain your answer.
12. Sketch larynx and explain its function in your own words.
Class–VIII (CHAPTER-13) SOUND Answers
1. (d) solids, liquids and gases.
Sound requires a medium to travel which can be a solid, a liquid or any gas.
2. (c) A man
Frequency of a sound is directly proportional to pitch. The pitch of a man is minimum among the given options.
3. (a) T (b) F (c) F (d) T (e) F (f) F (g) T
4. (a) Time taken by an object to complete one oscillation is called
time period.
(b) Loudness is determined by the amplitude of vibration. (c) The unit of frequency is hertz (Hz).
(d) Unwanted sound is called noise.
(e) Shrillness of a sound is determined by the frequency of vibration.
(Shrillness is also called pitch of the sound. Pitch is directly proportional to the frequency of vibration. Hence, shrillness is determined by the frequency of vibration.)
5. The no of oscillations per second is known as frequency.
Time period is the inverse of frequency of an object. Time Period
6. Time period is the inverse of frequency.
me perio
7. a) Dholak -Stretched membrane called as head.
When the head is beaten gently, the stretched membrane sets into vibration.
b) Sitar - strings.
When a string is plucked, it sets into vibration. c) Flute- Air.
When air is blown over its mouth, the air inside the pipe is set into vibration.
8. Noise is an unpleasant sound which is a result of irregular vibrations. Music is a sound which is pleasant to the ears. Yes, music can sometimes become noise.
For example, playing songs on loudspeakers at a very high volume becomes noise.
9. Following are the major sources of noise pollution
(i) Sounds of vehicles.
(ii Sounds of bursting of crackers and explosives. (iii) Sounds of loudspeaker, TVs, transistors.
(iv) Sounds of kitchen appliances.
(v) Sounds of desert coolers, air conditioners.
10. Noise pollution is harmful to humans in many ways. Constant exposure to noise pollution can create many health-related problems; like insomnia, hypertension and may even lead to loss of hearing.
11. I would suggest my parents to take the house which is three lanes away from the roadside rather than taking the house next to roadside as there will be more noise in the roadside house coming from the sound of vehicles.
12. Larynx is a part of the throat. It consists of two stretched membranes with some gap between them. As air passes through the larynx, the membranes or vocal cords vibrate and produce sound. That is why larynx is also known as
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