📚 586: Mastering Wave Properties for Edexcel IGCSE Science | Edexcel IGCSE 科学：掌握波的特性（586）
Waves are all around us, from the light we see and the sound we hear to the seismic tremors that shape our planet. In the Edexcel IGCSE Science syllabus, understanding waves is essential because it links together physics concepts that explain how energy travels without transferring matter. This article breaks down every key wave topic you need for your exams, helping you master terms, equations and real-world applications.
波无处不在，从我们看见的光、听到的声音，到塑造地球形态的地震波。在 Edexcel IGCSE 科学大纲中，理解波至关重要，因为它把解释能量如何传播而不转移物质的物理概念联系在一起。本文将逐一解析考试所需的每一个关键波动知识点，帮助你掌握术语、方程和实际应用。
1. What is a Wave? | 什么是波？
A wave is a disturbance that transfers energy from one place to another without transferring matter. For example, a pebble dropped into a pond creates ripples that move outward, but the water itself does not travel with the wave; it only oscillates up and down around a fixed point.
波是一种扰动，它将能量从一个地方传递到另一个地方，却不传递物质。例如，一颗石子投入池塘会激起向外扩散的涟漪，但水本身并未随波移动，只是围绕固定点上下振荡。
All waves can be described in terms of their amplitude, wavelength, frequency and speed. The medium (the substance the wave travels through) vibrates in a way that either follows the direction of energy transfer or is perpendicular to it, giving rise to two main types of waves.
所有波都可以用振幅、波长、频率和波速来描述。介质（波传播所经过的物质）的振动方式或者与能量传递方向一致，或者与之垂直，由此形成了两种主要类型的波。
2. Transverse and Longitudinal Waves | 横波与纵波
In a transverse wave, the oscillations are perpendicular to the direction of energy transfer. Light and water waves are transverse examples. A transverse wave has crests (high points) and troughs (low points). The distance between two consecutive crests or troughs is one wavelength.
在横波中，振动方向与能量传递方向垂直。光波和水波就是横波的例子。横波有波峰（高点）和波谷（低点）。两个相邻波峰或波谷之间的距离就是一个波长。
In a longitudinal wave, the oscillations are parallel to the direction of energy transfer. Sound waves and seismic P-waves are longitudinal. These waves consist of compressions (regions where particles are close together) and rarefactions (regions where particles are spread apart). The wavelength is the distance between the centres of two consecutive compressions or rarefactions.
而在纵波中，振动方向与能量传递方向平行。声波和地震 P 波就是纵波。这类波由压缩区（粒子密集的区域）和稀疏区（粒子分散的区域）组成。波长是两个相邻压缩区或稀疏区中心之间的距离。
Both types of waves can be modelled using diagrams, but you should practise drawing and labelling the key features: amplitude, wavelength, crest, trough, compression and rarefaction.
两种波都可以用图示来模拟，但你应该练习绘制并标注关键特征：振幅、波长、波峰、波谷、压缩区和稀疏区。
3. Key Wave Parameters: Amplitude, Wavelength, Frequency and Period | 关键参数：振幅、波长、频率和周期
The amplitude of a wave is the maximum displacement of a point on the wave from its undisturbed position. In a transverse wave, it is the height of a crest or depth of a trough measured from the centre line. Amplitude relates to the energy carried by the wave – a larger amplitude means more energy.
波的振幅是波上某点离开其平衡位置的最大位移。在横波中，它是从中心线测量的波峰高度或波谷深度。振幅与波携带的能量相关——振幅越大，能量越大。
Wavelength (λ) is the distance between two successive identical points on the wave, such as crest to crest or compression to compression. It is measured in metres (m).
波长（λ）是波上两个连续相同点之间的距离，例如波峰到波峰或压缩区到压缩区。它以米（m）为单位测量。
eciprocal of frequency: T = 1/f. If a wave has a frequency of 50 Hz, its period is 0.02 s.
频率（f）是每秒钟通过某一点的完整波的数量，以赫兹（Hz）为单位。周期（T）是一个完整波通过某点所需的时间，它是频率的倒数：T = 1/f。如果波的频率为 50 Hz，则周期为 0.02 s。
4. The Wave Equation: v = f × λ | 波速方程 v = f × λ
The speed of a wave (v) is related to its frequency (f) and wavelength (λ) by the equation:
波的速度（v）与其频率（f）和波长（λ）通过以下方程关联：
v = f × λ
ve has a frequency of 500 Hz and a wavelength of 0.68 m, then v = 500 × 0.68 = 340 m/s, which is the typical speed of sound in air.
其中 v 是波速，单位为米/秒（m/s），f 是频率，单位为赫兹（Hz），λ 是波长，单位为米（m）。该公式适用于所有类型的波，包括光波、声波和水波。使用方程时，必须将所有单位转换为正确的 SI 形式。例如，若某声波的频率为 500 Hz，波长为 0.68 m，则 v = 500 × 0.68 = 340 m/s，这就是空气中声速的典型值。
You should also be able to interpret graphs of wave displacement against time or distance to extract frequency and wavelength.
考题常要求将方程变形为 f = v / λ 或 λ = v / f。你还应能从波位移-时间图或位移-距离图中提取频率和波长。
5. Reflection of Waves | 波的反射
Reflection occurs when a wave bounces off a surface and changes direction. The law of reflection states that the angle of incidence equals the angle of reflection, both measured relative to the normal (an imaginary line perpendicular to the surface). Smooth surfaces produce clear reflections, while rough surfaces scatter the wave in many directions, causing diffuse reflection.
反射发生在波撞击表面并改变方向时。反射定律指出，入射角等于反射角，两者均相对于法线（一条垂直于表面的假想线）测量。光滑表面产生清晰的反射，而粗糙表面使波向多个方向散射，引起漫反射。
For light, you can investigate reflection using a ray box, a plane mirror and a protractor. You will find that the incident ray, reflected ray and normal all lie in the same plane. Sound also reflects – this explains why echoes are produced when sound waves bounce off large, hard surfaces.
对于光，你可以用光线盒、平面镜和量角器来研究反射。你会发现入射光线、反射光线和法线都在同一平面内。声音也会反射——这解释了为何声波从大型坚硬表面反弹时会产生回声。
6. Refraction of Waves | 波的折射
Refraction is the change in direction of a wave when it passes from one medium to another due to a change in its speed. If a wave enters a medium where it travels more slowly, it bends towards the normal; if it enters a medium where it travels faster, it bends away from the normal.
折射是波从一种介质进入另一种介质时由于速度变化而发生的方向改变。若波进入传播速度更慢的介质，它将向法线弯折；若进入传播速度更快的介质，则将远离法线弯折。
For light, passing from air into glass causes it to slow down and bend towards the normal. The amount of bending depends on the refractive index of the materials. With water waves, you can observe refraction in a ripple tank when waves enter a shallower region – the wavelength decreases and the wave direction changes. However, the frequency of the wave remains constant during refraction; only speed and wavelength alter.
对于光，从空气进入玻璃会使光速减慢并向法线弯折。弯折程度取决于材料的折射率。对于水波，在波纹箱中可以观察到当波进入较浅区域时发生折射——波长减小，波的方向改变。然而，折射过程中波的频率保持不变，只有波速和波长改变。
7. Diffraction of Waves | 波的衍射
Diffraction is the spreading out of waves when they pass through a gap or around an obstacle. The amount of diffraction depends on the size of the gap relative to the wavelength. If the gap size is comparable to the wavelength, the waves spread out significantly; if the gap is much larger, the spreading is minimal and the waves pass through with little change.
衍射是波穿过缝隙或绕过障碍物时发生的向外扩散现象。衍射的程度取决于缝隙尺寸与波长的相对大小。如果缝隙尺寸与波长相仿，波会显著扩散；若缝隙大得多，扩散很小，波几乎不变地穿过。
You can demonstrate diffraction of water waves using a ripple tank with two barriers, varying the gap width. Sound waves diffract around doorways, which is why you can hear someone in a corridor even when you cannot see them. Light also diffracts, but its wavelength is so small that diffraction is only noticeable with very narrow slits.
你可以使用波纹箱和两个障碍物，改变缝隙宽度来展示水波的衍射。声波会绕过门洞衍射，这就是你即使看不见走廊里的人也能听到他们声音的原因。光也会衍射，但由于其波长太短，只有在非常窄的狭缝下衍射才明显。
8. The Electromagnetic Spectrum | 电磁波谱
ight, c). The waves are grouped by their wavelength and frequency, from longest wavelength (lowest frequency) to shortest wavelength (highest frequency): radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays.
电磁波谱是一个连续的横波范围，所有电磁波在真空中都以相同速度 3.0 × 10⁸ m/s（光速 c）传播。这些波按波长和频率分组，从最长波长（最低频率）到最短波长（最高频率）依次为：无线电波、微波、红外线、可见光、紫外线、X 射线和伽马射线。
s to all EM waves. Because their speed is constant, as frequency increases, wavelength must decrease. Each section of the spectrum has distinct properties and uses:
关系式 c = f × λ 同样适用于所有电磁波。由于速度恒定，频率增加时波长必然减小。波谱的每一部分都有独特的性质和用途：
| Region / 波段 | Wavelength Range / 波长范围 | Uses / 用途 | Dangers / 危害 |
|---|---|---|---|
| Radio / 无线电波 | 10³ m to 10⁻¹ m | Broadcasting, communications / 广播、通信 | Generally low / 一般较低 |
| Microwaves / 微波 | 10⁻¹ m to 10⁻³ m | Cooking, satellite transmissions / 烹饪、卫星传输 | Internal heating of body tissue / 体内组织加热 |
| Infrared / 红外线 | 10⁻³ m to 7×10⁻⁷ m | Thermal imaging, remote controls / 热成像、遥控器 | Skin burns / 皮肤灼伤 |
| Visible light / 可见光 | 7×10⁻⁷ m to 4×10⁻⁷ m | Seeing, photography / 视觉、摄影 | Eye damage if too bright / 过亮可损伤眼睛 |
| Ultraviolet / 紫外线 | 4×10⁻⁷ m to 10⁻⁸ m | Fluorescent lamps, tanning / 荧光灯、日晒 | Skin cancer, eye damage / 皮肤癌、眼睛损伤 |
| X-rays / X 射线 | 10⁻⁸ m to 10⁻¹³ m | Medical imaging, security / 医学成像、安检 | Cancer, cell damage / 癌症、细胞损伤 |
| Gamma rays / 伽马射线 | <10⁻¹¹ m | Sterilising medical equipment, cancer therapy / 医疗设备灭菌、癌症治疗 | Cancer, genetic mutation / 癌症、基因突变 |
9. Sound Waves and Applications | 声波及其应用
Sound waves are longitudinal waves caused by vibrating objects. They require a medium (solid, liquid or gas) to travel; sound cannot travel through a vacuum. The speed of sound varies in different materials – it travels fastest in solids and slowest in gases because the particles are closer together in solids, passing vibrations more quickly.
声波是由物体振动产生的纵波。它们需要介质（固体、液体或气体）才能传播，声音无法在真空中传播。声速在不同材料中各异——在固体中最快，在气体中最慢，因为固体中粒子更密集，能更快地传递振动。
The typical speed of sound in air is about 340 m/s, but it can be measured experimentally using a simple method with two microphones connected to an oscilloscope or by timing echoes over a known distance. Sonar uses sound waves to detect underwater objects by measuring the time taken for echoes to return, a practical application of wave reflection.
空气中声速的典型值约为 340 m/s，可以通过用连接示波器的两个麦克风，或在已知距离上计时回声的方法进行实验测量。声呐利用声波通过测量回声返回所需时间来探测水下物体，这是波反射的实际应用。
Humans can hear frequencies between about 20 Hz and 20,000 Hz. Ultrasound refers to sound with frequencies higher than this range. It is used in medical imaging (pre-natal scanning) and industrial flaw detection because it can reflect off boundaries inside materials. Infrasound, below 20 Hz, can be produced by earthquakes and is monitored to study seismic activity.
人类能听到约 20 Hz 到 20,000 Hz 之间的频率。超声波指频率高于此范围的声音。它被用于医学成像（产前扫描）和工业探伤，因为它能在材料内部的边界上反射。低于 20 Hz 的次声波可由地震产生，并被监测以研究地震活动。
10. Seismic Waves and Earth Structure | 地震波与地球结构
Seismic waves are generated by earthquakes or explosions and travel through the Earth. There are two main types: P-waves (primary waves) and S-waves (secondary waves). P-waves are longitudinal and can travel through both solids and liquids, while S-waves are transverse and can only travel through solids. This difference provides crucial evidence for the structure of the Earth's interior.
地震波由地震或爆炸产生，并在地球内部传播。主要有两种类型：P 波（纵波）和 S 波（横波）。P 波是纵波，可以在固体和液体中传播；而 S 波是横波，只能在固体中传播。这种差异为地球内部结构提供了关键证据。
When seismometers around the world record the arrival times of P-waves and S-waves after an earthquake, scientists notice that S-waves are not detected on the opposite side of the Earth, indicating a liquid outer core. P-waves do arrive but are refracted, creating shadow zones. This pattern helped establish that the Earth has a solid inner core, a liquid outer core, a mantle and a crust.
当地震后全球各地的地震仪记录到 P 波和 S 波的到达时间时，科学家发现地球另一侧检测不到 S 波，这表明存在液态外核。P 波确实到达但被折射，形成了影区。这一模式帮助确定地球具有固态内核、液态外核、地幔和地壳。
These observations are a direct application of wave behaviour – speed changes, refraction, reflection and the inability of transverse waves to pass through liquids – to build a picture of our planet’s hidden layers.
这些观测结果是将波的行为——速度变化、折射、反射以及横波无法通过液体——直接应用于构建我们星球隐藏层图像的一个范例。
Published by TutorHao | Science Revision Series | aleveler.com
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