Sound Class 8 Extra Questions and Answers Science Chapter 13 PDF are solved by experts and will guide students in the right direction. Students can get how to tackle different questions easily by solving the Extra Questions for Class 8 Science Question bank on a regular basis.
Class 8 Science Chapter 13 Extra Questions and Answers Sound
Extra Questions for Class 8 Science Chapter 13 Sound with Answers
Sound Class 8 Extra Questions Very Short Answer Type
Question 1.
Name some of the musical instruments which are simply beaten or struck to produce music.
Answer:
Such instruments are manjira, ghatam, kartal, dholak, etc.
Question 2.
What part in humans produces sound?
Answer:
It is voice box in humans, that produces sound.
Question 3.
Can sound travel through solid also?
Answer:
Yes, the sound can travel through solids also.
Question 4.
What is to and fro motion of an object called?
Answer:
The to and fro motion of an object is called vibration or oscillatory motion.
Sound Class 8 Extra Questions Short Answer Type 1
Question 1.
What role does sound play in our life?
Answer:
The sound plays an important role in our life. It helps us to communicate with one another.
Question 2.
Define vibration. What is its other 7 name ?
Answer:
The to and fro or back and forth motion of an object is known as vibration. Its other name is oscillation or oscillatory motion.
Question 3.
How do dolphins and whales communicate?
Answer:
The sound can travel in water as it is also a medium for sound to travel. So, whales and dolphins, which live in water, can easily communicate there.
Question 4.
Why does sound travel through wood or metals?
Answer:
As wood and all metals are solid matters, and all solids are the media for sound to travel, so sound travels through wood or metals.
Question 5.
Why should we never put a sharp, pointed or hard things into our ears?
Answer:
If we put sharp, pointed or hard (things in our ear, the eardrum might get damaged. And damage to eardrum can cause deafness).
Question 6.
Define frequency of oscillation.
Answer:
The number of oscillations or vibrations produced per second is known as frequency of oscillation.
Question 7.
How is frequency of oscillation expressed?
Answer:
The frequency of oscillation is expressed in terms of hertz. Its symbol is Hz. A frequency of one Hz is one oscillation per second.
Question 8.
If an object oscillates 20 times in one second, what would be its frequency?
Answer:
As the frequency is the number of vibrations per second; so in this case, when, an object oscillates 20 times in one second, its frequency would be 20 Hz.
Question 9.
Can we differentiate sounds on the basis of their amplitudes and frequencies?
Answer:
Yes, with the help of amplitude and frequency we can differentiate two sounds easily.
Question 10.
Define amplitude. How is it expressed ?
Answer:
The displacement of the oscillating body is the measure of the amplitude of vibration of the body. It is expressed in terms of metre (m).
Question 11.
How is loudness of a sound determined ?
Answer:
The loudness of a sound is determined by its amplitude. When the amplitude of a vibration is large, the sound produced is loud, and in case of the smaller amplitude, the sound produced is feeble.
Question 12.
What is noise? Do you enjoy the sound produced by horns of buses and trucks? Why?
Answer:
The unpleasant sounds are called noise. We do not enjoy the sounds produced by the horns of buses and trucks because these sounds are loud and harsh and hende are unpleasant sounds.
Question 13.
What are the causes of hearing impairment ?
Answer:
Hearing impairment is generally the result of an ear disease, injury or degeneration of the hearing mechanism with age. The noise pollution also contribute to deafness.
Question 14.
How can one improve hearing impairment ? Is society and technology to contribute towards improving this defect ?
Answer:
Technological devices for the hearing impaired have made it possible for such persons to improve their quality of hearing. Society too, can do much to improve the living environment for the hearing impaired by minimising noise pollution.
Question 15.
What should be done to control noise pollution?
Answer:
To control noise pollution, we must control the sources of noise at home or in the surroundings. We should also plant trees in the surroundings.
Sound Class 8 Extra Questions Short Answer Type 2
Question 1.
What is noise pollution and what are the harms due to it? Mention any two methods to limit noise pollution.
Answer:
Noise pollution: Presence of excessive or unwanted sounds in the environment is called noise pollution.
Major causes of noise pollution are sounds of vehicles, explosions including bursting of crackers, machines, loudspeakers, etc.
Harms of noise pollution:
(a) The presence of excessive noise in the surroundings causes many health related problems like lack of sleep, hypertension, anxiety, etc.
(b) A person who is exposed to a loud sound continuously may get temporary or even permanent impairment of hearing.
Methods to control noise pollution :
(a) Use of automobile horns should be minimised.
(b) TV and music systems should be run at low volumes.
Question 2.
What are audible and inaudible sounds ? Describe.
Answer:
Audible sounds: Sounds of frequencies between 20 to 20,000 hertz.
Inaudible sounds:
(i) Sounds of frequencies less than 20 hertz. Such sounds are called infrasonic.
(ii) Sounds of frequencies more than 20,000 hertz. Such sounds are called ultrasonic.
Question 3.
What are the uses of ultrasound?
Answer:
Uses of ultrasound :
- The ultrasound or ultrasonic sound is used in investigating and tracking many medical problems.
- In industries, ultrasound is used for detecting flaws and cracks in metallic and other structures.
- Some operations, like bloodless surgery, can be done by applying this sound.
Question 4.
Write a short note on the children having impaired hearing.
Answer:
A child who has a moderately severe hearing loss and does not use a hearing aid will hear very little conversational speech, because speech develops as the direct result of hearing. A child with a moderately severe hearing loss may have defective speech, minimal expressive vocabulary and inadequate language structure. So, children with impaired hearing need special care. By learning sign language such children can communicate effectively.
Sound Class 8 Extra Questions Long Answer Type
Question 1.
Describe the construction and working of ears with diagram.
Answer:
We hear sound through our ears. The shape of the outer part of ear is like a funnel. When sound enters in it, it travels down a canal at the end of which a thin membrane is stretched tightly. It is called the eardrum.
Sound vibrations make the eardrums vibrate. The eardrum sends vibrations to the inner ear. From there, the signals go to the brain and we hear.
Question 2.
(a) Name the sound box in human being. Explain, how it works ?
(b) A body vibrates 100 times in 20 seconds. Calculate the time period and frequency.
Answer:
(a) The name of the voice box is larynx. The larynx or voice box is responsible for producing sounds in humans were. The voice box consists of two vocal chords. These chords are arranged in such a manner that there is a small gap between them. This small gap allows air to pass through. When we speak, air is forced into this small gap by the lungs. The vibrations in the vocal chords produces the sound.
(b) Number of vibrations = 100
Time taken = 20 s
Time taken to complete one vibration
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