Class 8 Science Chapter 14 – Sound | SCERT Assam (English Medium)
Class 8 Science Chapter 14 – Sound (SCERT Assam – English Medium)
Explore the science behind sound waves, their propagation, and applications. This chapter covers vibration concepts, human ear structure, and noise pollution with Assam-specific examples.
✅ Key Topics:
- How sound travels through different media
- Characteristics of sound (amplitude, frequency, time period)
- Structure and working of human ear
- Noise pollution sources in Assam (traffic, construction)
- Ultrasound and its medical applications
- Sound measurement in decibels
🎯 Ospin Academy Benefits:
- Animated sound wave diagrams
- Comparative tables (noise vs music)
- Important numerical problems on frequency
- YouTube videos demonstrating sound experiments
Score higher with our SCERT-aligned sound chapter notes and interactive content!
Class 8 Science (English Medium) PDF Solutions 2025-26 | SCERT Assam
Get the Class 8 Science (English Medium) PDF with detailed solutions, MCQs, and extra practice questions for SCERT Assam 2025-26.
Class 8 Science
Chapter – 14 Ospin Academy
Sound
TEXTBOOK EXERCISES
Q. 1. Choose the correct answer:
Sound can travel through:
(a) gasses only.
(b) solids only.
(c) liquids only.
(d) solids, liquids and gasses
Ans. (d) solids, liquids and gasses.
Q. 2. Voice of which of the following is likely to have minimum frequency:
(a) Baby girl.
(b) Baby boy.
(c) A man.
(d) A woman.
Ans. (a) Baby girl.
Q. 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)
Ans. True.
(b) The number of oscillations per second of a vibrating object is called its time period. (T/F)
Ans. False.
(c) If the amplitude of vibration is large, sound is feeble. (T/F)
Ans. False.
(d) For human ears, the audible range is 20 Hz to 20,000 Hz. (T/F)
Ans. True.
(e) The lower the frequency of vibration, the higher is the pitch. (T/F)
Ans. False.
(f) Unwanted or unpleasant sound is termed as music. (T/F)
Ans. True.
(g) Noise pollution may cause partial hearing impairment. (T/F)
Ans. True.
Q. 4 Fill in the blanks with suitable words:
(a) Time taken by an object to complete one oscillation is called _________.
Ans. time period.
(b) Loudness is determined by the _________ of vibration.
Ans. amplitude.
(c) The unit of frequency is __________.
Ans. hertz.
(d) Unwanted sound is called __________.
Ans. noise.
(e) Shrillness of a sound is determined by the __________ of vibration.
Ans. frequency.
Q. 5. A pendulum oscillates 40 times in 4 seconds. Find its time period and frequency.
Ans. Time taken by pendulum to complete 40 oscillation = 4 seconds.
Time taken by pendulum to complete
1 oscillation = 4/40 = 1/10 = 0.1 sec.
Time period of pendulum = 0.1 sec.
Frequency of pendulum
= 40 oscillation/4 time = 10 Hz.
Q. 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?
Ans. Time taken to complete 500 vibrations = 1 second
Time taken to complete 1 vibration = 1/500
= 0.002. Time period of vibration = 0.002 second.
Q. 7. Identify the part which vibrates to produce sound in the following instruments:
(a) Dholak.
Ans. Stretched membrane.
(b) Sitar.
Ans. Strings.
(c) Flute.
Ans. Air column.
Q. 8. What is the difference between noise and music? Can music become noise sometimes?
Ans.
|
Music |
Noise |
|---|---|
|
1. Sound which is pleasant to the ears is called music. |
1. Sound which is unpleasant to the ears is called noise. |
|
2. Vibrations are regular and periodic in music. |
2. Vibrations are irregular and non-periodic in noise. |
Music become noise sometimes when it crosses the bearable range of sound for our, ears.
Q. 9. List sources of noise pollution in your surroundings.
Ans. There are various sources which cause sound pollution in our surroundings like: Honking of horns, loud sounds of machines in factories, loud musics in parties and marriages, loud sound of T.V. or radio, loud sounds of domestic electronic appliances like mixer grinder etc., are some sources of noise in our environment.
Q. 10. Explain in what way noise pollution is harmful to humans?
Ans. (i) Noise pollution can cause temporary or permanent deafening.
(ii) It can cause many health related problems like high blood pressure.
(iii) It can cause mental illness due to lack of sleep.
Q. 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 to buy? Explain your answer.
Ans. I would suggest my parents to buy a house which is three lanes away from the roadside. It is because the house situated on the roadside will have the following disadvantages in comparison to the house three lanes away from roadside:
(i) Lot of noise due to passing of vehicles.
(ii) Smoke and dust produced due to traffic on road.
(iii) Sound of pressure horns at the time of traffic jams or during peak hours of the traffic.
Q. 12. Sketch larynx and explain its function in your own word.
Ans.
The human beings produce sound by using the larynx. Larynx is situated in our throat at the top of wind-pipe. The larynx contains two ligaments known as vocal cords. Sound is produced by the vibrations of vocal cords.
Q. 13. Lightening and thunder take place in the sky at the same time and at the same distance from us. Lightening is seen earlier and thunder is heard later. Can you explain.
Ans. Lightening and thundering take place simultaneously but we see light earlier than thunder because light travels faster than sound, so it reaches us before the sound does.
Class 8 Science Chapter 14 – Sound FAQs
Get Free NCERT PDFs
If you want to download free PDFs of any chapter, click the link below and join our WhatsApp group:
