同济大学：《大学物理》课程教学资源（电子教案，英文版）第九章 机械波（上）

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Agenda today 1 Transverse waves and longitudinal waves 2 The speed of waves, 3 wavelength,frequency,phase 4 wave function

Agenda today 1 Transverse waves and longitudinal waves 2 The speed of waves, 3 wavelength, frequency, phase 4 wave function

Particle and waves Type of waves: Mechanical Waves(机械波) Electromagnetic waves(电磁波) Matter waves (物质波)

Particle and waves Type of waves: Mechanical Waves（机械波） Electromagnetic waves（电磁波） Matter waves（物质波）

Transverse waves and longitudinal waves 波和纵波) 横波的产生 0 族馆： 波长：因 play Ostop ■C■么4 Transverse waves the direction of the particle's motion is perpendicular to the direction that waves propagate

Transverse waves and longitudinal waves（横 波和纵波） Transverse waves : the direction of the particle’s motion is perpendicular to the direction that waves propagate

纵播的产生 族福： 波长： play stop ■C值”- Longitudinal waves:the direction of particle's motion is the same direction that the waves travel

Longitudinal waves: the direction of particle’s motion is the same direction that the waves travel

Surface waves(表面波)： Water wave breaks when it approach the beach

Surface waves（表面波）: Water wave breaks when it approach the beach

The function for sinusoidal wave: 4o时 (x±ut)+p] Where means waves travel left; means waves travel right with speed u

( ) ] 2 ( , ) cos[    y x t  A x  ut  The function for sinusoidal wave: Where + means waves travel left; - means waves travel right with speed u

Some concepts about waves: Amplitude(振幅)：the maximum displacement that a particle can make in the medium. Peak and Valley(波峰与波谷)： Wavelength(波长)：the minimum distance between any identical point along the direction of wave propagation Period(周期)：the period of the particle in oscillation

Some concepts about waves: Amplitude(振幅）: the maximum displacement that a particle can make in the medium. Peak and Valley(波峰与波谷）: Wavelength（波长）:the minimum distance between any identical point along the direction of wave propagation Period（周期）：the period of the particle in oscillation

Frequency(频率)：the number of peaks(valleys)that pass a given point in a unit time interval. Angular frequency: Angular wave number: 2元 2π 0= k= T Speed of waves:the distance that waves travel in unit time. y=

Speed of waves: the distance that waves travel in unit time. T 1   T k u        Frequency（频率）:the number of peaks (valleys) that pass a given point in a unit time interval. Angular frequency: T   2  Angular wave number:  2 k 

Phase: Wave surface(波阵面)：the surface on which all the particles have the same phase Wave front（波前)：the first wave surface that the wave propagates Spherical Plane waves waves

Phase: Wave surface（波阵面）：the surface on which all the particles have the same phase Spherical waves Plane waves Wave front（波前）: the first wave surface that the wave propagates