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# Sound

## 02 Waves and Wave Motion

• Wave: A wave is a pattern of disturbance which travels through a medium due to repeated vibrations of the particles of the medium.
• The disturbance is handed over from one particle to the next.
• Sound is pictorially represented by a continuous succession of peaks and valleys.
• Wave Motion: The motion of the disturbance is called wave motion.

#### TYPES OF WAVES

Waves are of two types:

• Longitudinal waves
• Transverse waves

#### LONGITUDINAL WAVES

• These are the waves in which the particles of the medium vibrate along the direction of wave motion.
• The waves which travel along a spring (or slinky) it is pushed and pulled at one end, are longitudinal waves.
• A longitudinal wave consists of two attributes travelling through a medium:
• Compressions and
• Rarefactions
• Compression:
• It is a part of longitudinal wave.
• Compression is a region of high pressure.
• In compression, particles of the medium are closer to one another than they normally are.
• There is a momentary reduction in volume of the medium during compression.
• Rarefaction: It is a part of longitudinal wave. Rarefaction is a region of low pressure. In rarefaction the particles of the medium are farther apart than normal, and there is a momentary increase in the volume of the medium.

#### TRANSVERSE WAVES

• In transverse waves, the particles of the medium vibrate perpendicular to the direction of wave motion.
• Transverse waves can be produced only in solids and liquids but not in gases.
• A transverse wave travels horizontally in a medium, the particles of the medium vibrate up and down in the vertical direction.
• A transverse wave consists of
• Crests and
• Troughs
• Crest:  Crest is the ‘elevation’ in a transverse wave.
• Trough: Trough is the ‘depression’ in a transverse wave.