Waves Revision for GCSE WJEC Science | GCSE WJEC 科学：波 考点精讲

📚 Waves Revision for GCSE WJEC Science | GCSE WJEC 科学：波 考点精讲

Waves are a fundamental part of GCSE WJEC Science. Understanding wave types, properties and behaviours helps explain many everyday phenomena, from echoes and rainbows to mobile phone signals and earthquakes. This guide covers all the key concepts you need: transverse and longitudinal waves, the wave equation, reflection, refraction, diffraction, sound waves, seismic waves, the electromagnetic spectrum, and essential practical skills.

波是GCSE WJEC科学的基础内容。理解波的类型、性质和行为有助于解释从回声、彩虹到手机信号和地震等许多日常现象。本指南涵盖你需要掌握的所有核心概念：横波与纵波、波动方程、反射、折射、衍射、声波、地震波、电磁波谱以及必备的实验技能。

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1. What are Waves? | 什么是波？

Waves are disturbances that transfer energy from one place to another without transferring matter. Mechanical waves (such as sound and water waves) require a medium to travel through, whereas electromagnetic waves can travel through a vacuum.

波是将能量从一个地方传递到另一个地方的扰动，而不传递物质。机械波（如声波和水波）需要介质才能传播，而电磁波可以在真空中传播。

Every wave is characterised by oscillations or vibrations. The direction of these oscillations determines whether the wave is transverse or longitudinal.

每种波都由振动或振荡来描述。这些振动的方向决定了波是横波还是纵波。

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2. Transverse and Longitudinal Waves | 横波与纵波

In transverse waves, the oscillations are perpendicular to the direction of energy transfer. Examples include light, water waves, and all waves in the electromagnetic spectrum. Transverse waves have crests (highest points) and troughs (lowest points).

在横波中，振动方向与能量传递方向垂直。例如光波、水波以及电磁波谱中的所有波。横波具有波峰（最高点）和波谷（最低点）。

In longitudinal waves, the oscillations are parallel to the direction of energy transfer. Sound waves and seismic P-waves are longitudinal. They consist of compressions (regions of higher pressure) and rarefactions (regions of lower pressure).

在纵波中，振动方向与能量传递方向平行。声波和地震P波是纵波。它们由压缩区（高压区域）和稀疏区（低压区域）组成。

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3. Describing Waves: Amplitude, Wavelength, Frequency | 描述波：振幅、波长、频率

The amplitude of a wave is the maximum displacement from the undisturbed (rest) position. A wave with a larger amplitude carries more energy.

波的振幅是从未受扰动（平衡）位置的最大位移。振幅越大的波携带的能量越多。

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

波长 (λ) 是波上两个连续对应点之间的距离，例如从一个波峰到下一个波峰，或从一个压缩区到下一个压缩区。波长的单位是米 (m)。

Frequency (f) is the number of complete waves passing a fixed point per second. The unit of frequency is hertz (Hz). 1 Hz means one complete wave per second. Period (T) is the time for one complete wave to pass a point, measured in seconds. The two are related by:

T = 1 / f

频率 (f) 是每秒钟通过某固定点的完整波的数量。频率的单位是赫兹 (Hz)。1 Hz 表示每秒一个完整波。周期 (T) 是一个完整波通过某点所需的时间，以秒为单位。两者的关系为：

T = 1 / f

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4. The Wave Equation | 波动方程

The speed of a wave can be calculated if its frequency and wavelength are known. This is given by the wave equation:

v = f × λ

如果已知波的频率和波长，就可以计算波速。这由波动方程给出：

v = f × λ

Here, v is wave speed in metres per second (m/s), f is frequency in hertz (Hz), and λ is wavelength in metres (m). The equation can be rearranged to f = v / λ or λ = v / f. When using the equation, always make sure all distances are in metres.

其中 v 是以米/秒 (m/s) 为单位的波速，f 是以赫兹 (Hz) 为单位的频率，λ 是以米 (m) 为单位的波长。该方程可变形为 f = v / λ 或 λ = v / f。使用时务必确保所有距离单位统一为米。

Example: A sound wave has a frequency of 260 Hz and a wavelength of 1.3 m. Its speed is v = 260 × 1.3 = 338 m/s.

示例：某声波频率为 260 Hz，波长为 1.3 m，则其波速为 v = 260 × 1.3 = 338 m/s。

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5. Reflection of Waves | 波的反射

Reflection occurs when a wave strikes a boundary between two different media and bounces back. The angle of incidence (i) is equal to the angle of reflection (r), with both angles measured from the normal — a line perpendicular to the surface.

当波撞击两种不同介质之间的界面并反弹回来时，就发生了反射。入射角 (i) 等于反射角 (r)，两者都从法线（垂直于界面的线）量起。

Reflection can be observed with light in mirrors, sound echoes, and water waves hitting a wall. The wave’s speed, frequency and wavelength remain unchanged after reflection; only the direction changes.

反射可以在镜子中的光、声音回声和水波碰到墙壁时观察到。反射后波速、频率和波长保持不变；只有方向发生改变。

Smooth surfaces produce specular reflection, giving a clear image. Rough surfaces cause diffuse reflection, where the waves are scattered in many directions.

光滑表面产生镜面反射，形成清晰的像。粗糙表面导致漫反射，波会向多个方向散射。

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6. Refraction of Waves | 波的折射

Refraction is the change in direction of a wave when it crosses from one medium into another and changes speed. The frequency of the wave remains the same, but its speed and wavelength alter.

折射是波从一种介质进入另一种介质时速度

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