CBSE Class 9 Physics Sound
Production and Propagation of Sound
Sound is a wave motion, produced by a vibrating source.
A medium is necessary for the propagation of sound waves.
Sound is a longitudinal wave in which the particles of medium move along the direction of motion of wave.
Compression is the region of high pressure and rarefaction is the region of low pressure.Characteristics of Sound Waves
Reflection of Sound
Sound like light gets reflected at the surface of solid or a liquid and follows the same law as the reflection of light.
The persistence of sound due to repeated reflection and its gradual fading away is called reverberation of sound.
Echo is a repetition of sound due to the reflection of original sound by a large and hard obstacle.Ultrasound and Human Ear
SONAR stands for Sound Navigation and Ranging and it works on the principle of reflection of sound waves.
The audible range of hearing for average human beings is in the range of 20 Hz - 20 kHz.
Sound of frequency less than 20 Hz is known as infrasound and greater than 20 kHz is known as ultrasound.
