biology why do we fall ill 9 th class
CHAPTER 12 – “Sound”
KEY CONCEPTS [ *rating as per the significance of concept]
1
Production of Sound
****
2
Propagation of Sound
*****
3
Reflection of Sound
*****
4
Echo
****
5
Uses Of Multiple Reflection ***
Of Sound
6
Range of Hearing
***
7
Applications of Ultrasound
**
8
SONAR
**
9
Structure of Human Ear
****
1. Production of Sound
Sound is produced due to the vibration of objects. Vibration is the rapid to and fro motion of an object. Vibrating objects are the source of all sounds Irregular, chaotic vibrations produce noise Regular, controlled vibration can produce music All sound is a combination of pure frequencies
A stretched rubber band when plucked vibrates and produces sound.
2. Propagation of Sound
When an object vibrates, the particles around the medium vibrate. The particle in contact with the vibrating object is first displaced from its equilibrium position
The disturbance produced by the vibrating body travels through the medium but the particles do not move forward themselves.
A wave is a disturbance which moves through a medium by the vibration of the particles of the medium. So sound is considered as a wave.Sound waves Require medium for transmission.Sound waves are called mechanical waves. When a vibrating object moves forward, it pushes and compresses the air in front of it forming a region of high pressure called compression (C). When the vibrating object moves backward, it forms a region of low pressure called rarefaction (R).
125
A vibrating object producing a series of compressions (C) and rarefaction (R)
In these waves the particles move back and forth parallel to the direction of propagation of the disturbance. Such waves are called longitudinal waves.
There is another kind of waves called transverse waves. In these waves the particles oscillate up and down perpendicular to the propagation of the direction of disturbance.
Sound
KEY CONCEPTS [ *rating as per the significance of concept]
1
Production of Sound
****
2
Propagation of Sound
*****
3
Reflection of Sound
*****
4
Echo
****
5
Uses Of Multiple Reflection ***
Of Sound
6
Range of Hearing
***
7
Applications of Ultrasound
**
8
SONAR
**
9
Structure of Human Ear
****
1. Production of Sound
Sound is produced due to the vibration of objects. Vibration is the rapid to and fro motion of an object. Vibrating objects are the source of all sounds Irregular, chaotic vibrations produce noise Regular, controlled vibration can produce music All sound is a combination of pure frequencies
A stretched rubber band when plucked vibrates and produces sound.
2. Propagation of Sound
When an object vibrates, the particles around the medium vibrate. The particle in contact with the vibrating object is first displaced from its equilibrium position
The disturbance produced by the vibrating body travels through the medium but the particles do not move forward themselves.
A wave is a disturbance which moves through a medium by the vibration of the particles of the medium. So sound is considered as a wave.Sound waves Require medium for transmission.Sound waves are called mechanical waves. When a vibrating object moves forward, it pushes and compresses the air in front of it forming a region of high pressure called compression (C). When the vibrating object moves backward, it forms a region of low pressure called rarefaction (R).
125
A vibrating object producing a series of compressions (C) and rarefaction (R)
In these waves the particles move back and forth parallel to the direction of propagation of the disturbance. Such waves are called longitudinal waves.
There is another kind of waves called transverse waves. In these waves the particles oscillate up and down perpendicular to the propagation of the direction of disturbance.
Sound