Chapter 13 wave motion and sound Key words: Mechanical wave机械波 Electromagnetic wave电磁波 Transverse wave(横波) Longitudinal wave(纵波) crests(波峰) and troughs(波谷) Sinusoidal wave(正弦波) Traveling( moving, progressive)wave(行波 Standing( (stationary)wave(驻波) Stretched string(拉紧的线、弦线) Angular wave number(角波数 Interference of waves(波的干涉)Chapter 13 Wave Motion and Sound Key words: Mechanical wave 机械波 Electromagnetic wave 电磁波 Transverse wave( 横波) Longitudinal wave(纵波) crests (波峰) and troughs (波谷) Sinusoidal wave(正弦波) Traveling (moving, progressive) wave(行波) Standing (stationary) wave(驻波) Stretched string(拉紧的线、弦线) Angular wave number(角波数) Interference of waves(波的干涉)