Very Short Answers - Sound, Science, Class 8 Class 8 Notes | EduRev

Science Class 8

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Class 8 : Very Short Answers - Sound, Science, Class 8 Class 8 Notes | EduRev

The document Very Short Answers - Sound, Science, Class 8 Class 8 Notes | EduRev is a part of the Class 8 Course Science Class 8.
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VERY SHORT ANSWER TYPE QUESTIONS
 

Q. 1. What is sound?
Ans.
Sound is the medium by which we communicate with one another.
 

Q. 2. How is sound produced?
Ans.
Sound is produced by vibrating bodies.


Q. 3. Do all bodies can produce sound?
Ans.
No, all bodies cannot produce sound.


Q. 4. What do you feel when you touch a sound producing school bell?
Ans.
We feel the vibrations in the bell.


Q. 5. Touch the bell when it stops producing sound. Can you feel the vibrations?
Ans.
No, we cannot feel vibrations.
 

Q. 6. What do you understand by this?
Ans.
We understand that only vibrating bodies can produce sound.
 

Q. 7. What do you understand by vibrations?
Ans.
The back and forth motion of an object is called vibration.
 

Q. 8. In some cases we cannot see vibrations explain why is it so?
Ans.
When amplitude of vibrations is very small, then we cannot see them.


Q. 9. What is amplitude?
Ans.
The maximum displacement of a vibrating body on one side is called amplitude.
 

Q. 10. Name a musical instrument which produces sound by air column.
Ans.
Flute.
 

Q. 11. Name the sound producing organ in human.
Ans.
Larynx.


Q. 12. What is the other name of larynx?
Ans.
Larynx is also called voice box.


Q. 13. What are vocal cords?
Ans.
The cords stretched across the voice box or larynx are called vocal cords.
 

Q. 14. Do all animals produce sound by vocal cords?
Ans.
No, all animals do not produce sound by vocal cords.
 

Q. 15. On which quality of sound or voice depend?
Ans.
The quality of sound or voice depends on the looseness or tightness of vocal cords.
 

Q. 16. Do the length of vocal cords is same in men and women?
Ans.
No, the length of vocal cords is not same in men and women.
 

Q. 17. What is the length of vocal cords in men and women?
Ans.
The length of vocal cords in men and women is 20 mm and 15 mm respectively.
 

Q. 18. How does sound travel from one place to another?
Ans.
Sound travels through a material medium from one place to another.
 

Q. 19. Can sound travel through vacuum?
Ans.
No, sound cannot travel through vacuum.
 

Q. 20. What types of medium is required to travel sound?
Ans.
The medium may be solid, liquid or gas.
 

Q. 21. How do whales and dolphins hear the sound?
Ans.
Whales and dolphins live in water. They hear sound through water.
 

Q. 22. Name the organs in human which receives sound.
Ans.
Ears.
 

Q. 23. What is outer part of ear called?
Ans.
The outer part of the ear is called pinna. It is funnel shaped.
 

Q. 24. What is eardrum?
Ans.
A thin and stretched membrane is called eardrum.
 

Q. 25. What is oscillatory motion?
Ans.
The vibratory motion is also called oscillatory motion.
 

Q. 26. What do you mean by frequency?
Ans.
The number of oscillations in one second is called frequency.
 

Q. 27. Write the unit of frequency.
Ans.
The unit of frequency is hertz.


Q. 28. Define hertz.
Ans.
A frequency of one hertz is one oscillation per second.
 

Q. 29. What are the two main properties of a sound which help us to recognise sound?
Ans.
Amplitude and frequency are the two important properties of sound. 


Q. 30. Define time period.
Ans.
The time taken by a vibrating body to complete one oscillation is called  time period.
 

Q. 31. On which factor loudness of sound depend?
Ans.
The loudness of sound depends on the amplitude.
 

Q. 32. What is pitch or shrillness of a sound?
Ans.
The characteristics of sound which depends on its frequency is called pitch of a sound.
 

Q. 33. What is the hearing range of human ears?
Ans.
Hearing range of human ears is 20 Hz to 20,000 Hz.
 

Q. 34. What are frequencies of sound which are inaudible?
Ans.
Less than 20 Hz and more than 20,000 Hz are inaudible.
 

Q. 35. How does the amplitude affect the loudness of voice?
Ans.
Higher is the amplitude, louder is the voice.
 

Q. 36. Why the sound of a baby is feeble?
Ans.
The sound of a baby is feeble due to its small amplitude.
 

Q. 37. What frequencies are heard by dogs and cats?
Ans.
The dogs can hear up to 40,000 Hz frequencies while cats can hear up to 70,000 Hz frequencies.
 

Q . 38. What is ultrasound?
Ans.
The sound having frequency more than 20,000 Hz is called ultrasound.
 

Q. 39. What is noise?
Ans.
The loud sound which produces unpleasant sensation is called noise.
 

Q. 40. What do you mean by musical sound?
Ans.
The sound which produces pleasant sensation is called musical sound.
 

Q. 41. Give examples of noise and musical sound.
Ans.
The sound in classroom is noise while sound of any musical instrument is musical sound.
 

Q. 42. What do you mean by air pollution?
Ans.
Presence of unwanted gases and dust particles in air is called air pollution.
 

Q. 43. What is noise pollution?
Ans.
Presence of excessive or unwanted sounds in environment is called noise pollution.
 

Q . 44. What sources in home may lead to noise?
Ans.
Television, transistor, radio at high volume, desert coolers and air conditioners are the sources producing noise at home.
 

Q. 45. What is the unit of loudness?
Ans
. Decibel (dB).
 

Q. 46. What is the loudness of a normal conversation?
Ans.
60 dB. 


Q. 47. Write a common ill effect of noise pollution.
Ans.
The most common ill effect of noise pollution is temporary deafness.
 

Q. 48. Write any one method to control noise pollution.
Ans.
To grow more and more plants along the road sides.

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