CIE A-Level Physics: Waves and Superposition | CIE A-Level 物理：波动与叠加

📚 CIE A-Level Physics: Waves and Superposition | CIE A-Level 物理：波动与叠加

This revision guide covers the core CIE A-Level Physics waves topic, including progressive waves, wave parameters, polarisation, superposition, two-source interference, diffraction gratings and stationary waves. Master these ideas and you will be well prepared for both AS structured questions and A-Level synoptic papers.

本复习指南覆盖 CIE A-Level 物理波动部分的核心内容，包括行波、波参数、偏振、叠加、双源干涉、衍射光栅和驻波。掌握这些概念后，你将能从容应对 AS 结构题和 A-Level 综合试卷。

1. Progressive Waves and Wave Types | 行波与波的类型

A progressive wave transfers energy from one place to another without transferring matter. The source of a wave disturbs the medium or field, and this disturbance travels outwards. For CIE, you must distinguish transverse waves, in which particles oscillate perpendicular to the direction of energy transfer, from longitudinal waves, in which particles oscillate parallel to the direction of energy transfer.

行波把能量从一处传递到另一处，但不会传递物质。波源扰动介质或场，这种扰动向外传播。在 CIE 考试中，你必须区分横波和纵波：横波中质点的振动方向与能量传递方向垂直；纵波中质点的振动方向与能量传递方向平行。

Examples of transverse waves include electromagnetic waves, water surface waves and waves on a stretched string. Longitudinal waves include sound waves, ultrasound and compression waves in a slinky spring. A displacement-distance graph shows the shape of the wave at one instant; a displacement-time graph shows how one particle oscillates over time.

横波的例子包括电磁波、水面波和拉紧绳子上的波。纵波包括声波、超声波和弹簧中的压缩波。位移-距离图显示某一时刻波的形状；位移-时间图显示单个质点随时间振动的情况。

2. Key Wave Parameters: Wavelength, Frequency, Speed | 关键波参数：波长、频率、波速

You need precise definitions for A-Level. Wavelength λ is the minimum distance between two points in phase on a wave, for example two adjacent crests or two adjacent compressions. Frequency f is the number of complete oscillations per second, measured in hertz (Hz). Period T is the time for one complete oscillation, and T = 1/f.

A-Level 需要精确的定义。波长 λ 是波上两个同相位点之间的最小距离，例如两个相邻波峰或两个相邻压缩点。频率 f 是每秒完整振动的次数，单位是赫兹（Hz）。周期 T 是一次完整振动所需的时间，T = 1/f。

Amplitude A is the maximum displacement from the equilibrium position. Wave speed v is the distance travelled by the wave profile per unit time. It is determined by the medium, not by the frequency. Use the table below to check your definitions.

振幅 A 是质点离开平衡位置的最大位移。波速 v 是波形每单位时间传播的距离。波速由介质决定，而不是由频率决定。用下表检查你的定义。