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Ncert Solution | Ncert Solution for class 9th | NCERT solutions for Class 9 Science | NCERT SCIENCE CHAPTER 12 SOUND
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NCERT Solutions for Class 9 Science Chapter 12 Sound

NCERT Solutions for Class 9 Science Chapter 12 Sound are prepared by CBSE student eCARE expert to score good marks in class 9. This chapter contain many topics which are very important to score good in class 9. There are some important topic/Activity mentioned below- 

Topics and Sub Topics in Class 9 Science Chapter 12 Sound:

  1. Sound
  2. Production of Sound
  3. Propagation of Sound
  4. Reflection of Sound
  5. Range of Hearing
  6. Applications of Ultrasound
  7. Structure of Human Ear

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Some questions are asked by class 9 students related to Science

Question 1. How does the sound produced by a vibrating object in a medium reach your ear?
Answer: Air is the commonest material through which sound propagates. When vibrating objects, like prongs of a tuning fork move forward, they push the molecules of the air in front of them. This in turn compresses the air, thus creating a region of high pressure and high density called compression. This compression in the air travels forward. When the prongs of the tuning fork move backward, they create a region of low pressure in the air, commonly called rarefaction.
This region has low pressure, low density, and more volume. As the tuning fork continues to vibrate, the regions of compression in the air alternate with the regions of rarefaction. These regions alternate at the same place. The energy of vibrating tuning fork travels outward. This energy which reaches the ears, makes the eardrums to vibrate and thus we hear sound


Question

 Explain how sound is produced by your school bell.
Answer: Air is the commonest material through which sound propagates. When school bell is rung, it pushes the molecules of the air in front of it. This in turn compresses the air, thus creating a region of high pressure and high density called compression. This compression in the air travels forward. When the bell moves back, it creates a region of low pressure in the air, commonly called rarefaction. This region has low pressure, low density, and more volume. As the bell continues to vibrate, the regions Of compression in the air alternate with the regions of rarefaction. These regions alternate at the same place. The energy of vibrating bell travels outward. This energy which reaches the ears, makes the eardrums to vibrate and thus we hear sound.

Question

Why are sound waves called mechanical waves ?
Answer: Some mechanical energy is required to make an object vibrate. Sound energy cannot be produced on its own. The mechanical energy Of vibrating object travels through a medium and finally reaches the ear. Therefore, the sound waves are called mechanical waves.