📚 KS3 CIE Waves: Exam Questions and Mark Scheme | KS3 CIE 波浪：考试题与评分方案
Waves questions at KS3 CIE level are not just about remembering definitions. Examiners mark the precision of your scientific language, your ability to read diagrams, and your use of the wave speed equation. This revision guide breaks down the common question types and shows you exactly what a mark scheme rewards.
KS3 CIE 波浪题不仅考查定义记忆。评分人看重科学语言的准确性、读图能力以及波速公式的运用。本复习指南分解常见题型，并展示评分方案具体给分点。
1. What the Exam Tests | 考试考查什么
Most KS3 CIE waves papers test three core skills: describing wave motion with correct terminology, reading information from wave diagrams, and calculating wave speed, frequency or wavelength. Marks are awarded for using the exact scientific words in the mark scheme, not just for showing a general idea.
大多数 KS3 CIE 波浪试卷考查三项核心技能：用正确术语描述波动、从波形图中读取信息、以及计算波速、频率或波长。评分时要求使用评分方案中的准确科学词汇，而不仅仅是表达大致意思。
You should also expect questions that ask you to compare transverse and longitudinal waves, explain reflection or refraction, and describe how sound or light behaves. Each command word tells you how much detail is needed.
你还会遇到比较横波与纵波、解释反射或折射、描述声音或光的行为等题目。每个指令词都提示你需要写出多少细节。
2. Longitudinal vs Transverse Waves | 纵波与横波
In a transverse wave, the oscillations are perpendicular to the direction of energy transfer. Light, water ripples and waves on a rope are transverse waves. In a longitudinal wave, the oscillations are parallel to the direction of energy transfer. Sound waves are longitudinal.
在横波中，振动方向与能量传递方向垂直。光、水波和绳子上的波都是横波。在纵波中，振动方向与能量传递方向平行。声波是纵波。
The mark scheme often awards one mark for saying ‘oscillations are perpendicular’ for transverse waves and one for saying ‘oscillations are parallel’ for longitudinal waves. Always include the word ‘energy transfer’ or ‘wave direction’ to make your answer complete.
评分方案通常给横波的 ‘振动方向垂直’ 一分，给纵波的 ‘振动方向平行’ 一分。答题时一定要写出 ‘能量传递’ 或 ‘波的传播方向’，答案才完整。
- Transverse: oscillations are at right angles to wave direction.
- 横波：振动方向与波的传播方向成直角。
- Longitudinal: oscillations are along the same line as wave direction.
- 纵波：振动方向与波的传播方向在同一直线上。
3. Amplitude, Wavelength and Frequency | 振幅、波长与频率
Amplitude is the maximum displacement of a point on the wave from its rest position. It is measured in metres. Wavelength, symbol λ, is the distance between two adjacent crests or two adjacent compressions. Frequency is the number of complete waves passing a point per second, measured in hertz (Hz).
振幅是波上某点离开平衡位置的最大位移，单位为米。波长（符号 λ）是两个相邻波峰或两个相邻密部之间的距离。频率是每秒通过某点的完整波的个数，单位为赫兹（Hz）。
The period of a wave is the time taken for one complete wave to pass a point. It relates to frequency by the equation f = 1 / T. If a question gives you the period, convert it to frequency before using the wave speed equation.
波的周期是一个完整波通过某点所需的时间。它与频率的关系是 f = 1 / T。如果题目给出周期，要先换算成频率，再代入波速公式。
f = 1 ÷ T
Mark schemes often test whether you can identify amplitude and wavelength correctly on a diagram. Amplitude is always measured vertically from the rest line to a crest or trough, while wavelength is measured horizontally from crest to crest or trough to trough.
评分方案常考查你是否能在图上正确识别振幅和波长。振幅总是从平衡线垂直量到波峰或波谷，而波长是从一个波峰到下一个波峰或一个波谷到下一个波谷的水平距离。
4. The Wave Speed Equation | 波速公式
The relationship between wave speed, frequency and wavelength is given by the wave speed equation. You must be able to rearrange it to find any of the three quantities.
波速、频率和波长之间的关系由波速公式表示。你必须会变形公式，求出三个量中的任意一个。
v = f × λ
Where v is wave speed in metres per second (m/s), f is frequency in hertz (Hz), and λ is wavelength in metres (m). To find frequency, use f = v ÷ λ. To find wavelength, use λ = v ÷ f.
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）。求频率用 f = v ÷ λ，求波长用 λ = v ÷ f。
A very common mark scheme instruction is to award one mark for correct substitution and one mark for the correct answer with the correct unit. If you miss the unit, you often lose the final mark even if the number is right.
评分方案中一个常见要求是：正确代入公式得一分，答案正确且单位正确再得一分。如果漏写单位，即使数字正确，通常也会失去最后一分。
5. Reflection of Waves | 波的反射
Reflection occurs when a wave bounces off a surface. For light, sound and water waves, the law of reflection states that the angle of incidence equals the angle of reflection. Both angles are measured from the normal, which is an imaginary line at 90° to the surface.
反射是波从表面反弹回来的现象。对于光波、声波和水波，反射定律指出入射角等于反射角。两个角都从法线量起，法线是与表面成 90° 的假想线。
In exam answers, always state that the angles are measured from the normal, not from the surface. A mark scheme may say ‘angle of incidence = angle of reflection’ and ‘angles measured from the normal’ as two separate marking points.
答题时一定要说明角是从法线量起，而不是从表面量起。评分方案可能把 ‘入射角等于反射角’ 和 ‘角从法线量起’ 分成两个给分点。
Diagram questions may ask you to draw the reflected ray. Make sure the reflected ray is on the opposite side of the normal, at the same angle to the normal as the incident ray, and includes an arrow pointing away from the surface.
作图题可能要求你画出反射光线。确保反射光线位于法线另一侧，与法线的夹角和入射光线相同，并且箭头方向远离表面。
6. Refraction and Wave Fronts | 折射与波前
Refraction is the change in direction of a wave when it enters a new medium at an angle, caused by a change in wave speed. When light enters glass or water from air, it slows down and bends towards the normal. When it leaves back into air, it speeds up and bends away from the normal.
折射是波以一定角度进入新介质时传播方向发生改变的现象，原因是波速发生了变化。当光从空气进入玻璃或水时，速度减慢，向法线偏折；当光离开玻璃或水回到空气时，速度加快，偏离法线。
Mark schemes often reward the phrases ‘bends towards the normal’ and ‘bends away from the normal’. You should also mention that the wave speed changes, because speed is the scientific reason for refraction.
评分方案常奖励 ‘向法线偏折’ 和 ‘偏离法线’ 这些短语。你还应提到波速发生变化，因为波速改变是折射的科学原因。
If a question shows wave fronts, remember that wave fronts get closer together when a wave slows down. This is because wavelength decreases when speed decreases, while frequency stays the same.
如果题目给出波前图，记住波速减慢时波前会靠得更近。这是因为波速减小时波长也减小，而频率保持不变。
7. Sound Waves and the Ear | 声波与耳朵
Sound waves are longitudinal waves caused by vibrating objects. They need a medium to travel through, such as a solid, liquid or gas. Sound cannot travel through a vacuum because there are no particles to vibrate.
声波是由物体振动产生的纵波。它们需要通过介质传播，例如固体、液体或气体。声音不能在真空中传播，因为真空中没有粒子可以振动。
In the ear, sound waves make the eardrum vibrate. These vibrations are passed through the small bones to the cochlea, which converts them into electrical signals sent to the brain. KS3 questions usually ask for the eardrum and cochlea rather than all the tiny bones.
在耳朵中，声波使鼓膜振动。这些振动通过小骨传递到耳蜗，耳蜗将振动转化为电信号传给大脑。KS3 题目通常要求写出鼓膜和耳蜗，而不要求写出所有小骨名称。
Sound travels faster in solids than in liquids, and faster in liquids than in gases. A mark scheme may accept ‘particles are closer together in solids, so vibrations pass more quickly’ as an explanation.
声音在固体中比在液体中传播快，在液体中比在气体中传播快。评分方案可能接受 ‘固体中粒子靠得更近，因此振动传递更快’ 作为解释。
8. Light Waves and the Electromagnetic Spectrum | 光波与电磁波谱
Light is a transverse wave. Unlike sound, light can travel through a vacuum. Light waves travel at a speed of about 3 × 10⁸ m/s in a vacuum. This very high speed is often used in calculations.
光是横波。与声音不同，光可以在真空中传播。光在真空中的速度约为 3 × 10⁸ m/s。这个极高的速度常用于计算。
Visible light is part of the electromagnetic spectrum. The order from lowest frequency to highest frequency is: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays and gamma rays. KS3 mark schemes usually expect you to know the order and one or two uses or dangers of each region.
可见光是电磁波谱的一部分。从最低频率到最高频率的顺序是：无线电波、微波、红外线、可见光、紫外线、X 射线和伽马射线。KS3 评分方案通常要求你掌握这个顺序，以及每个波段的一两种用途或危害。
All electromagnetic waves are transverse and can travel through a vacuum. They transfer energy from one place to another. A common exam question asks why light can travel from the Sun to Earth but sound cannot; the answer is that light does not need particles, but sound does.
所有电磁波都是横波，并且可以在真空中传播。它们将能量从一个地方传递到另一个地方。常见考题问为什么光能从太阳传到地球而声音不能；答案是光不需要粒子，而声音需要粒子。
9. Sample Question 1: Wave Diagram | 样题 1：波形图
Sample question 1
A student makes a wave on a rope. The diagram shows the rope at one instant.
样题 1
一名学生在绳子上制造了一个波。图示为某一瞬间绳子的形状。
- a) Name the type of wave shown on the rope. [1]
- b) State what the distance P represents. [1]
- c) State what the distance Q represents. [1]
- d) If 8 complete waves pass a point in 4 seconds, calculate the frequency of the wave. [2]
Mark scheme
| Part | Answer | Marks |
|---|---|---|
| a) | Transverse wave | 1 |
| b) | Amplitude | 1 |
| c) | Wavelength | 1 |
| d) | f = number of waves ÷ time = 8 ÷ 4 = 2 Hz; award 1 mark for substitution, 1 mark for answer with unit | 2 |
Notice that in part d, the mark scheme requires the unit hertz. Writing ‘2’ without ‘Hz’ scores only one of the two marks. This is a very common place to lose marks.
注意在 d 部分，评分方案要求写出单位赫兹。只写 ‘2’ 而不写 ‘Hz’ 只能得两分中的一分。这是非常常见的失分点。
10. Sample Question 2: Wave Speed Calculation | 样题 2：波速计算
Sample question 2
A water wave has a wavelength of 2.5 m and a frequency of 0.8 Hz. Calculate the speed of the water wave. Include the correct unit.
样题 2
一个水波的波长为 2.5 m，频率为 0.8 Hz。计算该水波的波速，并写出正确单位。
v = f × λ = 0.8 × 2.5 = 2.0 m/s
Award 1 mark for correct substitution into v = f × λ. Award 1 mark for the correct numerical answer. Award 1 mark for the correct unit m/s. If the unit is missing, the maximum score is 2 marks.
正确代入 v = f × λ 得 1 分；数值正确得 1 分；单位 m/s 正确得 1 分。如果漏写单位，最多只能得 2 分。
Another common calculation gives wave speed and wavelength, then asks for frequency. For example, if speed is 12 m/s and wavelength is 4 m, then f = v ÷ λ = 12 ÷ 4 = 3 Hz. Always write the rearranged equation before substituting numbers.
另一种常见计算是给出波速和波长，要求频率。例如波速为 12 m/s，波长为 4 m，则 f = v ÷ λ = 12 ÷ 4 = 3 Hz。代入数字前一定要先写出变形后的公式。
11. Mark Scheme Key Words and Command Words | 评分方案关键词与指令词
Different command words require different types of answers. ‘State’ means give a short answer with no explanation. ‘Describe’ means say what happens or what you observe. ‘Explain’ means give a scientific reason, often using particles or energy transfer. ‘Calculate’ means show your working and give the unit.
不同的指令词要求不同类型的答案。’State’ 表示写出简短答案，不需要解释；’Describe’ 表示说明发生了什么或观察到什么；’Explain’ 表示给出科学原因，通常用粒子或能量传递来解释；’Calculate’ 表示写出计算过程并给出单位。
| Key word | Meaning in waves | 中文含义 |
|---|---|---|
| Oscillation | Repeated back-and-forth movement | 来回往复运动 |
| Medium | Material a wave travels through | 波传播的介质 |
| Vacuum | Space with no particles | 没有粒子的空间 |
| Normal | Imaginary line at 90° to a surface | 与表面成 90° 的假想线 |
| Perpendicular | At right angles | 成直角 |
| Parallel | Along the same direction | 沿同一方向 |
Using these key words accurately is the fastest way to match the mark scheme. For example, writing ‘the wave travels at right angles to the vibration’ is not as strong as ‘the oscillations are perpendicular to the direction of energy transfer’.
准确使用这些关键词是快速匹配评分方案的最佳方法。例如，写 ‘波与振动方向成直角’ 不如写 ‘振动方向与能量传递方向垂直’ 得分更有把握。
12. Common Mistakes and Revision Tips | 常见错误与复习建议
One common mistake is confusing amplitude with wavelength. Amplitude is half the vertical height of a wave, while wavelength is the horizontal distance for one full cycle. Always check which line is the rest position on the diagram.
常见错误之一是混淆振幅和波长。振幅是波垂直高度的一半，而波长是一个完整周期对应的水平距离。读图时一定要先确定哪条线是平衡位置。
Another common mistake is forgetting to convert units. Wavelength may be given in centimetres but the wave speed equation needs metres. Before substituting, convert cm to m by dividing by 100.
另一个常见错误是忘记换算单位。波长可能以厘米为单位给出，但波速公式需要使用米。代入前应先将厘米除以 100 换算成米。
Many students lose marks by not showing their working in calculations. Even if the final answer is wrong, a correct substitution into v = f × λ can still earn a mark. Always write the equation first, then substitute numbers, then write the answer with a unit.
许多学生在计算题中因不写过程而失分。即使最终答案错误，只要正确代入 v = f × λ，仍然可以得到过程分。一定要先写公式，再代入数字，最后写出带单位的答案。
For revision, practise drawing and labelling transverse waves, rearranging the wave speed equation, and writing two-mark explanations about why sound cannot travel in a vacuum. Use past CIE-style questions and then compare your answers to the mark scheme line by line.
复习时建议练习绘制并标注横波、变形波速公式，以及写出关于声音不能在真空中传播的两分解释题。使用 CIE 风格真题，然后逐行对照评分方案检查自己的答案。
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