📚 IGCSE CIE Physics: Last-Minute Exam-Crash Notes | IGCSE CIE 物理：考前冲刺笔记
Struggling to remember all those formulas and definitions the night before your IGCSE CIE Physics exam? This set of concise, bilingual revision notes covers every major topic in the syllabus — from mechanics and energy to waves, electricity, and radioactivity. Use it to pinpoint weak spots, reinforce key concepts, and walk into the exam hall feeling prepared.
在 IGCSE CIE 物理考试前一晚还在努力记住所有公式和定义？这套简洁的中英双语复习笔记涵盖了考纲中的每一个大主题——从力学、能量到波、电学和放射性。用它来查缺补漏、巩固关键概念，自信地走进考场。
1. Measurement and Units | 测量与单位
Always record every measurement with the correct SI unit and an appropriate number of significant figures. Length (metre, m), mass (kilogram, kg), time (second, s), current (ampere, A), and temperature (kelvin, K) are the fundamental base quantities.
每次测量都要记录正确的国际单位制和适当的有效数字。长度（米，m）、质量（千克，kg）、时间（秒，s）、电流（安培，A）和温度（开尔文，K）是基本物理量。
A scalar has magnitude only (e.g. speed, distance, mass). A vector has both magnitude and direction (e.g. velocity, displacement, force). Always draw vectors with arrows and calculate the resultant using the parallelogram or tip-to-tail method.
标量只有大小（如速率、路程、质量）。矢量既有大小又有方向（如速度、位移、力）。始终用箭头表示矢量，并使用平行四边形法或三角形法计算合矢量。
2. Mechanics: Motion and Forces | 力学：运动与力
Speed = distance ÷ time (v = d / t). Acceleration = change in velocity ÷ time (a = (v − u) / t). For uniform acceleration: v = u + at, s = ½(u+v)t, s = ut + ½at², v² = u² + 2as. Remember to take direction into account for velocity – deceleration is negative acceleration.
速率 = 路程 ÷ 时间（v = d / t）。加速度 = 速度变化量 ÷ 时间（a = (v − u) / t）。匀加速运动公式：v = u + at，s = ½(u+v)t，s = ut + ½at²，v² = u² + 2as。注意速度要考虑方向——减速即为负加速度。
Newton’s First Law: an object remains at rest or in uniform motion unless acted on by a resultant force. Second Law: F = ma. Third Law: every action has an equal and opposite reaction (acting on different objects).
牛顿第一定律：物体在不受合力作用时保持静止或匀速直线运动。第二定律：F = ma。第三定律：作用力与反作用力大小相等、方向相反（作用在不同物体上）。
Weight W = mg (g ≈ 9.8 m/s² on Earth). Centre of mass is the point where the whole weight seems to act. Terminal velocity occurs when air resistance balances weight; net force becomes zero.
重量 W = mg（地球上 g ≈ 9.8 m/s²）。重心是物体所受重力作用的等效点。当空气阻力与重力平衡时达到终端速度，此时合力为零。
3. Energy, Work, and Power | 能量、功与功率
Work done = force × distance moved in direction of force (W = Fd). Kinetic energy Eₖ = ½mv². Gravitational potential energy Eₚ = mgh. The principle of conservation of energy: energy cannot be created or destroyed, only transferred or converted.
功 = 力 × 在力的方向上移动的距离（W = Fd）。动能 Eₖ = ½mv²。重力势能 Eₚ = mgh。能量守恒定律：能量不能凭空产生或消失，只能转移或转化。
Power = work done ÷ time (P = W / t) or energy transferred per unit time. Efficiency = (useful energy output ÷ total energy input) × 100%. In energy‑transfer diagrams, width of the arrows represents the amount of energy.
功率 = 功 ÷ 时间（P = W / t）或单位时间内转移的能量。效率 =（有用的输出能量 ÷ 总输入能量）× 100%。在能量转移图中，箭头的宽度表示能量的多少。
Renewable sources: solar, wind, hydroelectric, wave, tidal, geothermal, biomass. Non‑renewable: fossil fuels, nuclear (uranium). Advantages and disadvantages linked to reliability, running cost, start‑up time and environmental impact must be known.
可再生能源：太阳能、风能、水力发电、波浪能、潮汐能、地热能、生物质能。不可再生能源：化石燃料、核能（铀）。需要了解它们在可靠性、运行成本、启动时间和环境影响方面的优缺点。
4. Thermal Physics | 热物理
Absolute zero (0 K = −273 °C) is the temperature at which particles have minimum kinetic energy. Temperature measures the average kinetic energy of particles. Internal energy is the sum of random kinetic energy and intermolecular potential energy.
绝对零度（0 K = −273 °C）是粒子动能最低的温度。温度衡量粒子平均动能的大小。内能是粒子无规则运动的动能与分子间势能的总和。
Specific heat capacity c: energy needed to raise 1 kg of a substance by 1 °C, Q = mcΔθ. Specific latent heat L: energy needed to change state of 1 kg without temperature change, Q = mL. During melting or boiling, temperature stays constant while internal energy increases.
比热容 c：使 1 kg 物质升高 1 °C 所需的能量，Q = mcΔθ。比潜热 L：使 1 kg 物质在温度不变时改变状态所需的能量，Q = mL。熔化或沸腾时，温度保持不变，内能增加。
Conduction: transfer of heat through solids by vibrating particles and free electrons. Convection: occurs in fluids, where less dense, hotter fluid rises. Radiation: transfer by infrared electromagnetic waves, can travel through a vacuum. A good absorber is also a good emitter.
传导：通过固体中振动的粒子和自由电子传递热量。对流：发生在流体中，密度较小的热流体上升。辐射：通过红外电磁波传递热量，可在真空中传播。良好的吸收体同时也是良好的发射体。
5. Properties of Waves | 波的性质
Waves transfer energy without transferring matter. Transverse waves: vibrations are perpendicular to direction of energy travel (e.g. light, water waves). Longitudinal waves: vibrations are parallel to direction of energy travel (e.g. sound).
波传递能量而不传递物质。横波：振动方向垂直于能量传播方向（如光波、水波）。纵波：振动方向平行于能量传播方向（如声波）。
Key terms: amplitude (maximum displacement from rest), wavelength λ, frequency f (number of waves per second, Hz), period T = 1/f. Wave speed v = fλ. Reflection, refraction and diffraction are all wave behaviours.
关键术语：振幅（离开平衡位置的最大位移）、波长 λ、频率 f（每秒完整波数，Hz）、周期 T = 1/f。波速 v = fλ。反射、折射和衍射都是波的特性。
Refraction happens because wave speed changes when entering a different medium; frequency stays the same. Diffraction is the spreading of a wave around a gap or obstacle; it is most significant when the gap size is comparable to the wavelength.
折射是因为波进入不同介质时波速改变；频率保持不变。衍射是波绕过障碍物或穿过缝隙时发生的扩散现象，当缝隙大小与波长相近时衍射最显著。
6. Light and Sound | 光与声
Law of reflection: angle of incidence i = angle of reflection r. Images in a plane mirror are virtual, upright, laterally inverted and the same distance behind the mirror as the object is in front.
反射定律：入射角 i = 反射角 r。平面镜所成的像是虚像、正立、左右颠倒，且像到镜面的距离等于物到镜面的距离。
Refraction of light follows Snell’s law: n = sin i / sin r. Total internal reflection occurs when light travels from a denser to a less dense medium and the angle of incidence exceeds the critical angle c, given by n = 1 / sin c. Optical fibres use total internal reflection.
光的折射遵循斯涅尔定律：n = sin i / sin r。全内反射发生在光从光密介质射向光疏介质，且入射角大于临界角 c 时，n = 1 / sin c。光纤利用全内反射原理。
The electromagnetic spectrum: radio, microwaves, infrared, visible light, ultraviolet, X‑rays, gamma rays (in order of increasing frequency). All travel at speed c = 3.0 × 10⁸ m/s in a vacuum.
电磁波谱：无线电波、微波、红外线、可见光、紫外线、X 射线、γ 射线（按频率递增排列）。所有电磁波在真空中的速度均为 c = 3.0 × 10⁸ m/s。
Sound is a longitudinal wave, requires a medium, and its speed varies: about 330 m/s in air, faster in liquids and solids. Pitch depends on frequency; loudness depends on amplitude. Ultrasound has frequency above 20 kHz and is used for scanning and cleaning.
声音是纵波，需要介质传播，速度在空气中约 330 m/s，在液体和固体中更快。音调取决于频率，响度取决于振幅。超声波频率高于 20 kHz，用于扫描和清洗。
7. Electricity: Charge and Current | 电学：电荷与电流
Charge Q is measured in coulombs (C); current I = Q / t (ampere, A). Conventional current flows from positive to negative, opposite to electron flow. In a series circuit, current is the same everywhere; in parallel, it splits between branches.
电荷 Q 单位是库仑（C）；电流 I = Q / t（安培，A）。传统电流方向为正电荷流动方向，与电子流动方向相反。串联电路中电流处处相等；并联电路中电流在各支路中分配。
Potential difference (p.d.) V = energy transferred per unit charge, V = W / Q (volt, V). Electromotive force (e.m.f.) is the energy supplied by a source per unit charge. Resistance R = V / I (ohm, Ω).
电势差 V = 单位电荷转移的能量，V = W / Q（伏特，V）。电动势是电源提供给每单位电荷的能量。电阻 R = V / I（欧姆，Ω）。
Ohm’s law: for a metallic conductor at constant temperature, V ∝ I. Filament lamps have increasing resistance with temperature; diodes allow current in only one direction.
欧姆定律：对于恒温下的金属导体，V ∝ I。灯丝灯泡的电阻随温度升高而增大；二极管只允许电流单向通过。
8. Electrical Circuits and Practical Skills | 电路与实验技能
Series: resistance adds up Rₜ = R₁ + R₂ + … ; current same; p.d. splits. Parallel: total resistance 1/Rₜ = 1/R₁ + 1/R₂ + … ; current splits; p.d. same across each branch.
串联：总电阻相加 Rₜ = R₁ + R₂ + …；电流相同；电压分配。并联：总电阻倒数相加 1/Rₜ = 1/R₁ + 1/R₂ + …；电流分配；各支路电压相等。
Power dissipation P = IV = I²R = V² / R. The ammeter is connected in series; the voltmeter in parallel. Electrical energy E = P t = IVt.
电功率 P = IV = I²R = V² / R。安培表串联接入，伏特表并联接入。电能 E = P t = IVt。
Potential divider: Vₒᵤₜ = [R₂ / (R₁+R₂)] × Vᵢₙ. A variable resistor or thermistor can create a sensor circuit, e.g. a thermostat.
分压电路：Vₒᵤₜ = [R₂ / (R₁+R₂)] × Vᵢₙ。可变电阻器或热敏电阻可构成传感器电路，如恒温器。
Common practical investigations include: measuring resistance using voltmeter‑ammeter method, investigating I‑V characteristics, and finding the resistivity of a wire using R = ρL/A. Always identify the independent, dependent and controlled variables.
常见实验探究包括：伏安法测电阻、研究 I‑V 特性、以及利用 R = ρL/A 测导线电阻率。始终要确定自变量、因变量和控制变量。
9. Electromagnetism | 电磁效应
When a current‑carrying conductor is in a magnetic field, it experiences a force. Fleming’s left‑hand rule: thumb = force, first finger = field (N → S), second finger = current (+ to −). Force F = BIL for a straight conductor perpendicular to the field.
通电导体在磁场中会受到力的作用。弗莱明左手定则：拇指—受力方向，食指—磁场方向（N 到 S），中指—电流方向（正到负）。与磁场垂直的直导线受力 F = BIL。
A simple electric motor uses a coil in a magnetic field and a split‑ring commutator to reverse current every half turn, maintaining continuous rotation.
简易电动机将线圈置于磁场中，并用换向器每半圈改变电流方向，从而维持连续转动。
Electromagnetic induction: when a conductor cuts magnetic field lines, a p.d. is induced across its ends. Generator effect: moving a magnet into a coil or rotating a coil in a magnetic field produces an alternating current (AC).
电磁感应：当导体切割磁感线时，其两端会产生感应电动势。发电机效应：将磁铁插入线圈或让线圈在磁场中转动，会产生交流电。
A transformer uses two coils on a soft iron core. Vₚ/Vₛ = Nₚ/Nₛ. For an ideal transformer, input power = output power, so VₚIₚ = VₛIₛ. Step‑up increases voltage and decreases current; step‑down does the opposite.
变压器由铁芯上的两个线圈组成。Vₚ/Vₛ = Nₚ/Nₛ。对于理想变压器，输入功率 = 输出功率，因此 VₚIₚ = VₛIₛ。升压变压器提高电压、降低电流；降压变压器相反。
10. Atomic Physics and Radioactivity | 原子物理与放射性
The nuclear atom: nucleus contains protons and neutrons, surrounded by electrons in shells. Proton number Z defines the element; nucleon number A = protons + neutrons. Isotopes have same Z but different A.
原子核模型：原子核由质子和中子组成，核外电子分层排布。质子数 Z 决定元素种类；核子数 A = 质子数 + 中子数。同位素的质子数相同但核子数不同。
Alpha particle: helium nucleus ⁴₂He, highly ionising, stopped by paper. Beta particle: fast electron ⁰₋₁e, moderately ionising, stopped by a few mm of aluminium. Gamma ray: electromagnetic, weakly ionising, reduced by thick lead or concrete.
α 粒子：氦原子核 ⁴₂He，电离能力很强，一张纸即可阻挡。β 粒子：高速电子 ⁰₋₁e，电离能力中等，几毫米铝板可阻挡。γ 射线：电磁波，电离能力弱，需厚铅板或混凝土才能减弱。
Radioactive decay is random. The count rate or number of undecayed nuclei halves every half‑life. Use half‑life graphs to find the time for activity to drop to a certain fraction. Background radiation must be subtracted first.
放射性衰变是随机的。计数率或未衰变原子核的数量每经过一个半衰期减少一半。使用半衰期图像可找出活度下降到某一分数所需的时间。必须首先扣除本底辐射。
Nuclear fission: a large nucleus splits into two smaller nuclei, releasing neutrons and energy. Nuclear fusion: two light nuclei join to form a heavier nucleus, releasing huge energy (the Sun’s process). Both involve mass converted to energy, E = mc².
核裂变：一个重核分裂为两个较轻的原子核，释放出中子和能量。核聚变：两个轻核结合成一个较重的原子核，释放巨量能量（太阳的能量来源）。两者都涉及质量转化为能量，E = mc²。
11. Space Physics | 空间物理
The Solar System consists of the Sun, planets, moons, asteroids and comets. Planets move in elliptical orbits; the gravitational force provides the centripetal force. Orbital speed v = 2πr / T and is higher for planets closer to the Sun.
太阳系由太阳、行星、卫星、小行星和彗星组成。行星沿椭圆轨道运行；万有引力提供向心力。轨道速度 v = 2πr / T，距太阳越近的行星轨道速度越快。
The life cycle of a star: nebula → protostar → main sequence (fusion of H to He) → red giant or red supergiant → white dwarf/neutron star/black hole depending on initial mass. The Sun is a main‑sequence star.
恒星的演化周期：星云 → 原恒星 → 主序星（氢聚变为氦） → 红巨星或红超巨星 → 白矮星/中子星/黑洞，取决于初始质量。太阳目前是一颗主序星。
Redshift provides evidence that the Universe is expanding. The greater the redshift, the faster a galaxy is moving away. The Big Bang theory states that the Universe began from a single point. Cosmic microwave background radiation supports this.
红移现象为宇宙膨胀提供了证据。红移越大，星系远离我们的速度越快。大爆炸理论认为宇宙从一个点开始膨胀。宇宙微波背景辐射支持了该理论。
12. Exam Tips and Command Words | 考试技巧与指令词
Read the question carefully: underline the command word. ‘State’ requires a short, factual answer; ‘Describe’ requires a step‑by‑step account; ‘Explain’ asks for a reason using a scientific principle; ‘Calculate’ means show your working and give the unit.
仔细审题：划出指令词。‘State’ 需要简短的客观事实；‘Describe’ 需要逐步描述；‘Explain’ 要求用科学原理解释原因；‘Calculate’ 表示写出演算过程并给出单位。
Always convert to SI units before substituting into formulas. Check that your final answer has the correct unit and a sensible number of significant figures (usually 2 or 3). On graphical questions, label axes with quantity and unit, choose a proper scale, and draw a smooth curve or best‑fit straight line.
代入公式前务必转换成国际单位制。检查最终答案是否有正确单位和合理的有效数字（通常 2 或 3 位）。作图题要标出坐标轴对应的物理量和单位，选择合适的比例，画平滑的曲线或最佳拟合直线。
For ‘design an experiment’ questions, always state the apparatus, the method stepwise, the measurements to take, how to make the experiment fair (controlled variables), and how to process the data (e.g. plot a graph, use a given equation).
遇到“设计实验”题，务必说明所需器材、逐步方法、测量哪些量、如何保证实验公平（控制变量）以及如何处理数据（例如绘制图像、使用给定公式）。
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