IGCSE Edexcel Physics: Waves Key Points | IGCSE Edexcel 物理：波 考点精讲

📚 IGCSE Edexcel Physics: Waves Key Points | IGCSE Edexcel 物理：波 考点精讲

Waves are fundamental in physics, transferring energy from one place to another without transferring matter. In the IGCSE Edexcel specification, waves cover topics such as wave properties, light, sound, and the electromagnetic spectrum. This article summarises the key concepts, equations, and exam tips to help you master the topic.

波是物理学中的基础概念，它能将能量从一个地方传递到另一个地方，而无需传递物质。在 IGCSE Edexcel 大纲中，波的内容涵盖波的性质、光、声以及电磁波谱。本文总结了关键概念、公式和考试技巧，助你掌握这一主题。

1. Types of Waves: Transverse vs Longitudinal | 波的类型：横波与纵波

Transverse waves are waves where the particles of the medium vibrate perpendicular to the direction of energy transfer. Examples include all electromagnetic waves, ripples on water, and S-waves (secondary seismic waves). The peaks and troughs are characteristic features.

横波是指介质质点的振动方向与能量传递方向垂直的波。例子包括所有电磁波、水波和 S 波（地震横波）。其特征是波峰和波谷。

Longitudinal waves are waves where particles vibrate parallel to the direction of energy transfer. Sound waves in air and P-waves (primary seismic waves) are longitudinal. They consist of compressions and rarefactions.

纵波是质点振动方向与能量传递方向平行的波。空气中的声波和 P 波（地震纵波）都是纵波。它们由密集区和稀疏区组成。

2. Describing Waves: Amplitude, Wavelength, Frequency, Speed | 波的描述：振幅、波长、频率、波速

The amplitude of a wave is the maximum displacement of a particle from its rest position. In transverse waves, it is the height of a crest or depth of a trough from the equilibrium line. Amplitude relates to the energy carried by the wave; larger amplitude means more energy.

振幅是质点离开平衡位置的最大位移。在横波中，就是从平衡位置到波峰或波谷的距离。振幅与波携带的能量有关；振幅越大，能量越多。

Wavelength (λ) is the distance between two consecutive corresponding points on a wave, e.g., crest to crest or compression to compression. It is measured in metres (m).

波长（λ）是波上两个相邻相同点之间的距离，例如从波峰到波峰或从密集区到密集区。单位是米（m）。

Frequency (f) is the number of complete waves passing a point per second. It is measured in hertz (Hz). Period (T) is the time taken for one complete wave to pass a point; T = 1/f.

频率（f）是每秒通过某点的完整波的数量，单位是赫兹（Hz）。周期（T）是一个完整波经过某点所需的时间；T = 1/f。

Wave speed (v) is the speed at which the wave energy travels. In a given medium, it is constant for a particular wave type.

波速（v）是波能量传播的速度。在给定介质中，特定类型的波速是恒定的。

3. The Wave Equation (v = fλ) | 波动方程 (v = fλ)

The wave equation is the core mathematical relationship for waves: v = f × λ. It relates wave speed (v, in m/s), frequency (f, in Hz), and wavelength (λ, in m).

v = f × λ

波动方程是波的核心数学关系：v = f × λ。它联系了波速（v，单位 m/s）、频率（f，单位 Hz）和波长（λ，单位 m）。

When waves travel from one medium into another, their frequency remains unchanged, but speed and wavelength change proportionally. For electromagnetic waves, v = c = 3.0 × 10⁸ m/s in vacuum.

波从一种介质进入另一种介质时，其频率保持不变，但波速和波长成比例改变。对于电磁波，真空中 v = c = 3.0 × 10⁸ m/s。

You can also use the frequency-period relation: f = 1/T and T = 1/f. Make sure you can rearrange these equations confidently for calculations.

你还可使用频率与周期的关系：f = 1/T 和 T = 1/f。务必熟练地重新排列这些公式以进行计算。

4. Reflection and Refraction | 反射与折射

Reflection occurs when waves bounce off a surface. The law of reflection states that the angle of incidence equals the angle of reflection, both measured from the normal. Smooth surfaces produce specular reflection; rough surfaces cause diffuse scattering.

波碰到表面时会发生反射。反射定律指出，入射角等于反射角，两者均从法线量起。光滑表面产生镜面反射；粗糙表面引起漫反射。

Refraction is the change in direction of waves as they pass from one medium to another due to a change in wave speed. If a light wave slows down (entering a denser medium), it bends towards the normal; if it speeds up, it bends away from the normal. This is why a straw appears bent in water.

折射是波由于速度改变而从一种介质进入另一种介质时发生的方向变化。如果光波减速（进入光密介质），它会偏向法线；如果加速，则远离法线。这就是吸管在水中看起来弯曲的原因。

Refraction follows Snell’s law, but for IGCSE you must be able to describe and predict the direction of bending qualitatively using wavefront diagrams and the normal.

Published by TutorHao | IGCSE Physics Revision Series | aleveler.com

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