SEBA Class 8 Science Chapter 14 Sound Solutions English Medium to each chapter is provided in the list so that you can easily browse through different chapters SEBA Class 8 Science Chapter 14 Sound Question Answer and select need one. SEBA Class 8 Science Chapter 14 Sound Solutions Download PDF. SEBA Class 8 Science Texbook Solutions English Medium.
SEBA Class 8 Science Chapter 14 Sound
Also, you can read the NCERT book online in these sections Solutions by Expert Teachers as per Central Board of Secondary Education (CBSE) Book guidelines. SEBA Class 8 General Science Textual Solutions in English are part of All Subject Solutions. Here we have given Class 8 Science Textbook Question Answer, SEBA Class 8 Science English Medium Textbook Solutions for All Chapters, You can practice these here.
Sound
Chapter: 14
PART – II
EXERCISE
Choose the correct answer.
1. Sound can travel through:
(a) Gases only.
(b) Solids only.
(c) Liquids only.
(d) Solids, liquids and gases.
Ans: (d) Solids, liquids and gases.
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: (c) A man.
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: False.
(g) Noise pollution may cause partial hearing impairment (T/F)
Ans: True.
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 (Hz).
(d) Unwanted sound is called ___________.
Ans: Noise.
(e) Shrillness of a sound is determined by the _________ of vibration.
Ans: Frequency.
5. A pendulum oscillates 40 times in 4 seconds. Find its time period and frequency.
Ans: A pendulum makes 40 oscillations in 4 seconds. The time period is the time it takes to complete one oscillation. So,
Time period = 4/40 = 0.1 seconds.
The frequency is the number of oscillations per second. So,
Frequency = 40/4 = 10 Hz.
6. The sound from a mosquito is produced when it vibrates its wings at an average rate of 50 vibrations per second. What is the time period of the vibration?
Ans: A mosquito vibrates its wings 50 times in one second. This means its frequency is 50 Hz. The time period is the time for one vibration.
Time Period = 1/50 = 0.02 seconds.
So, the mosquito takes 0.02 seconds to complete one wing vibration.
7. Identify the part which vibrates to produce sound in the following instruments.
(a) Dholak.
Ans: In a Dholak, the stretched membrane vibrates when struck.
(b) Sitar.
Ans: In a Sitar, the strings vibrate when plucked.
(c) Flute.
Ans: In a Flute, the air column inside the flute vibrates when air is blown.
8. What is the difference between noise and music? Can music become noise sometimes?
Ans: Music is a pleasant sound produced by instruments like the piano, guitar, or flute. Noise, on the other hand, is an unpleasant or unwanted sound produced by things like vehicle horns, crackers, or machines. However, music can turn into noise if played at a very high volume or from many sources at once, making it disturbing.
9. List sources of noise pollution in your surroundings.
Ans: List sources of noise pollution in my surroundings are:
(i) Honking of vehicles.
(ii) Loudspeakers.
(iii) Construction work.
(iv) TV or music at high volume.
(v) Factory machines.
10. Explain in what way noise pollution is harmful to human.
Ans: Harmful Effects of Noise Pollution on Humans:
(i) Causes Headaches and Stress: Loud and constant noise can lead to mental tension and physical discomfort.
(ii) Disturbs Sleep: Noise at night can prevent proper rest and lead to fatigue.
(iii) Reduces Concentration: It becomes difficult to focus on studies or work in a noisy environment.
(iv) Leads to Hearing Problems: Very loud sounds over time can damage the ears and cause partial or permanent hearing loss.
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.
Ans: I would suggest my parents buy the house that is three lanes away from the roadside.
This is because:
(i) It will be less noisy, as traffic noise is lower away from the main road.
(ii) The air will be cleaner with less smoke and dust from vehicles.
(iii) It will be safer, especially for children, as there will be less risk from traffic.
12. Sketch larynx and explain its function in your own words.
Ans:
The larynx is also called the voice box. It helps us to talk by producing sound using the vocal cords. It also lets air pass to the lungs and prevents food from entering the windpipe by closing with a flap called the epiglottis.
13. Lightning and thunder take place in the sky at the same time and at the same distance from us. Lightning is seen earlier and thunder is heard later. Can you explain why?
Ans: Lightning and thunder happen at the same time, but we see the lightning before we hear the thunder. That’s because light travels much faster than sound. Light reaches our eyes almost instantly. But sound travels slower, so it takes more time to reach our ears.
So, even though both occur together, we see the lightning first, and hear the thunder a few seconds later.
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