📚 IGCSE CIE Physics: End-of-Term Revision Guide | IGCSE CIE 物理：期末复习提纲
This revision guide covers the essential topics for IGCSE CIE Physics, summarising key concepts, formulas, and definitions to help you prepare for end-of-term exams. Each section presents core ideas in pairs of English and Chinese explanations, followed by concise equations and practical tips.
本复习提纲涵盖 IGCSE CIE 物理的核心主题，总结关键概念、公式和定义，以帮助备考期末考试。每节以中英文配对讲解呈现核心思路，并提供简明方程与实用提示。
1. Motion (Kinematics) | 运动（运动学）
locity is a vector (magnitude and direction). Average speed = total distance / total time.
运动使用速率、速度和加速度来描述。速率是标量（仅有大小），速度是矢量（有大小和方向）。平均速率 = 总路程 / 总时间。
Acceleration is the rate of change of velocity: a = (v – e acceleration means speeding up, negative acceleration (deceleration) means slowing down.
加速度是速度变化的快慢：a = (v – u) / t，其中 u 为初速度，v 为末速度。正加速度表示加速，负加速度（减速度）表示减速。
v = u + at s = ut + ½at² v² = u² + 2as
Distance–time graphs: the gradient gives speed. A horizontal line means stationary; a straight sloping line means constant speed; a curve means acceleration.
距离–时间图：梯度给出速率。水平线表示静止；倾斜直线表示恒定速率；曲线表示加速。
Speed– eleration, and the area under the graph gives distance travelled. For free fall near Earth's surface, acceleration due to gravity g ≈ 9.8 m/s².
速度–时间图：梯度给出加速度，图下面积给出所行距离。在地表附近自由落体，重力加速度 g ≈ 9.8 m/s²。
2. Forces and Dynamics | 力与动力学
A force is a push or pull that can change an object's speed, direction, or shape. Newton's First Law: an object remains at rest or in uniform motion unless acted upon by a resultant force.
力是推或拉，可以改变物体的速度、方向或形状。牛顿第一定律：物体若无合力作用，将保持静止或匀速直线运动。
Newton' ltant force F = m × a. Force is measured in newtons (N), mass in kg, acceleration in m/s².
牛顿第二定律：合力 F = m × a。力的单位是牛顿 (N)，质量单位 kg，加速度单位 m/s²。
F = m × a
Newton's Third Law: when object A exerts a force on object B, object B exerts an equal and opposite force on object A. Friction opposes motion and can be reduced by lubrication or streamlining.
牛顿第三定律：当物体 A 对物体 B 施力时，物体 B 对 A 施加大小相等、方向相反的力。摩擦力阻碍运动，可通过润滑或流线型设计减小。
n a closed system, total momentum before a collision equals total momentum after (conservation of momentum).
动量 p = m × v，是矢量。在封闭系统中，碰撞前的总动量等于碰撞后的总动量（动量守恒）。
fety features like seat belts and air bags increase the time of impact, reducing the force.
冲量 = 动量变化 = F × t。安全带、安全气囊等安全装置延长碰撞时间，从而减小作用力。
3. Mass, Weight, and Density | 质量、重量与密度
location. Weight is the gravitational force on an object: W = m × g, measured in newtons.
质量是物体所含物质的量，单位 kg，不随位置改变。重量是作用在物体上的重力：W = m × g，单位牛顿。
W = m × g
/m³ or g/cm³. 1 g/cm³ = 1000 kg/m³. An object floats if its density is less than the fluid's density.
密度 ρ = m / V，常用单位 kg/m³ 或 g/cm³。1 g/cm³ = 1000 kg/m³。物体密度小于流体密度时会上浮。
You can measure density of a regular solid with a ruler and balance, and of an irregular solid with a measuring cylinder (displacement method) and balance. For a liquid, measure mass of a known volume.
规则固体可用直尺和天平测密度；不规则固体可用量筒（排水法）和天平测密度。液体则测量已知体积的质量。
4. Energy, Work, and Power | 能量、功与功率
Energy is the ability to do work and is measured in joules (J). Forms include kinetic, potential (gravitational, elastic), thermal, chemical, nuclear, and light.
能量是做功的能力，单位焦耳 (J)。形式包括动能、势能（重力势能、弹性势能）、热能、化学能、核能和光能。
F × d (when force and displacement are in same direction). Energy transferred = work done.
做功 W = F × d（当力与位移同向时）。转移的能量 = 所做的功。
W = F × d KE = ½mv² GPE = mgh
Power P = work done / time taken = energy transferred / time, unit watt (W), 1 W = 1 J/s.
功率 P = 做功 / 所用时间 = 转移的能量 / 时间，单位瓦特 (W)，1 W = 1 J/s。
ric current, or by a force. Efficiency = (useful output energy / total input energy) × 100%.
能量可通过加热、波、电流或力来转移。效率 = (有用输出能量 / 总输入能量) × 100%。
Renewable sources include solar, wind, wave, tidal, hydroelectric, geothermal, and biomass. Non-renewable: fossil fuels and nuclear fuel. Generating electricity often involves turning a turbine connected to a generator.
可再生能源包括太阳能、风能、波浪能、潮汐能、水力发电、地热和生物质能。不可再生：化石燃料与核燃料。发电通常涉及转动与发电机相连的涡轮机。
5. Pressure | 压强
/m². A large force on a small area gives high pressure; a small force on a large area gives low pressure.
压强 p = F / A，单位帕斯卡 (Pa) 或 N/m²。大力作用于小面积产生高压强；小力作用于大面积产生低压强。
p = F / A
quid density, g is gravitational field strength. Pressure at a given depth acts equally in all directions.
在液体中，压强随深度增加：p = hρg，h 为深度，ρ 为液体密度，g 为重力场强度。同一深度处压强向各方向等大。
Atmospheric pressure can be measured with a barometer. It decreases with altitude. A manometer measures fluid pressure difference.
大气压强可用气压计测量，随高度升高而减小。U形管压力计可测量流体压强差。
Hydraulic systems use Pascal' ied to an enclosed fluid is transmitted undiminished. Force multiplier: F₂ / F₁ = A₂ / A₁.
液压系统利用帕斯卡原理：施加于封闭流体的压强会大小不变地传递。力的倍增：F₂ / F₁ = A₂ / A₁。
6. Thermal Physics | 热物理学
average kinetic energy of particles, measured in degrees Celsius (°C) or Kelvin (K). 0 K = –273 °C is absolute zero.
温度是粒子平均动能的量度，单位摄氏度 (°C) 或开尔文 (K)。0 K = –273 °C 为绝对零度。
latent heat L is energy needed to change state per kg without temperature change: Q = m L.
比热容 c 是使 1 kg 物质升高 1 °C 所需的能量：Q = m c Δθ。比潜热 L 是每千克物质在温度不变时改变状态所需的能量：Q = m L。
Q = m c Δθ Q = m L
Conduction occurs mainly in solids, where particles vibrate and pass on energy; metals are good conductors. Convection occurs in fluids due to density changes when heated. Radiation is the transfer of thermal energy by infrared waves and can occur in a vacuum.
导热主要发生在固体中，粒子振动并传递能量；金属是良导体。对流因加热后密度变化而发生于流体中。热辐射通过红外波传递热能，可在真空中进行。
A thermocouple and a liquid-in-glass thermometer are common thermometers. The liquid thermometer works by thermal expansion; its sensitivity, range, and linearity depend on the liquid and bore.
热电偶和玻璃液体温度计是常见温度计。液体温度计利用热胀冷缩原理；其灵敏度、量程和线性取决于液体和毛细管。
7. Waves Properties | 波的性质
Waves transfer energy without transferring matter. In transverse waves, particles vibrate perpendicular to wave direction (e.g., light, water waves). In longitudinal waves, particles vibrate parallel to wave direction (e.g., sound).
波传递能量而不传递物质。横波中，质点振动方向与波传播方向垂直（如光、水波）。纵波中，质点振动方向与波传播方向平行（如声波）。
ed v = f λ, where f is frequency and λ is wavelength. Frequency is measured in hertz (Hz).
波速 v = f λ，其中 f 为频率，λ 为波长。频率单位赫兹 (Hz)。
v = f λ
change speed at a boundary and bend, described by the refractive index n = sin i / sin r.
反射：入射角等于反射角。折射发生在波在边界处改变速度并弯曲时，由折射率 n = sin i / sin r 描述。
Diffraction is the spreading of waves around obstacles or through gaps; it is greatest when the wavelength is comparable to the gap size. All wave types can diffract.
衍射是波绕过障碍物或通过狭缝时的扩展现象；当波长与缝隙尺寸相近时衍射最明显。所有波都能发生衍射。
8. Light | 光
that travels at 3.0 × 10⁸ m/s in a vacuum. It can be reflected, refracted, and dispersed.
光是横电磁波，在真空中速度为 3.0 × 10⁸ m/s。光可被反射、折射和色散。
ane mirror forms a virtual, upright, laterally inverted image the same size as the object.
反射定律：入射光线、反射光线与法线共面；入射角 i 等于反射角 r。平面镜成虚像、正立、横向反转且与物体等大。
Refraction: light bends towards the normal when entering a denser medium and away from the normal when entering a less dense medium. Total internal reflection occurs when the angle of incidence exceeds the critical angle and light travels from denser to less dense medium.
折射：光进入光密介质时向法线偏折，进入光疏介质时远离法线偏折。当光从光密介质射向光疏介质且入射角大于临界角时，发生全内反射。
s depending on object distance. The lens equation: 1/f = 1/u + 1/v. Magnification = v / u.
凸（会聚）透镜使平行光线会聚到焦点；根据物距可成实像或虚像。透镜方程：1/f = 1/u + 1/v。放大率 = v / u。
White light dispersed by a prism produces a spectrum (red, orange, yellow, green, blue, indigo, violet) because different colours have different speeds in glass.
白光通过棱镜色散产生光谱（红、橙、黄、绿、蓝、靛、紫），因为不同颜色在玻璃中速度不同。
9. Sound | 声音
Sound is a longitudinal wave caused by vibrating objects. It needs a medium (solid, liquid, gas) to travel and cannot pass through a vacuum.
声音是由物体振动产生的纵波。它需要介质（固、液、气）传播，不能在真空中传递。
The speed of sound in air is about 330 m/s; it is faster in solids and liquids. Pitch depends on frequency; loudness depends on amplitude.
空气中声速约 330 m/s；在固体和液体中更快。音调取决于频率；响度取决于振幅。
Echo is the reflection of sound; sonar uses echoes to measure distance. Ultrasound is sound above 20 000 Hz, used for cleaning, medical imaging, and sonar.
回声是声音的反射；声呐利用回声测距。超声波是频率超过 20 000 Hz 的声音，用于清洗、医学成像和声呐。
A microphone converts sound energy to electrical signals; a loudspeaker does the reverse. The human hearing range is approximately 20 Hz to 20 kHz.
麦克风将声能转换为电信号；扬声器则反之。人耳可听频率范围约 20 Hz 至 20 kHz。
10. Electricity and Circuits | 电学与电路
A). Conventional current flows from positive to negative terminal; electron flow is opposite.
电荷单位库仑 (C)。电流 I = Q / t，单位安培 (A)。常规电流方向从正极到负极；电子流动与之相反。
I = Q / t
the energy supplied per unit charge by the source. Resistance R = V / I, unit ohm (Ω). Ohm's law applies when resistance is constant at constant temperature.
电势差 V = W / Q，单位伏特 (V)。电动势是电源每单位电荷提供的能量。电阻 R = V / I，单位欧姆 (Ω)。当温度不变且电阻恒定时，遵循欧姆定律。
V = I × R P = I × V = I² R = V² / R
ame across branches; total current is the sum of branch currents; 1/Rₜ = 1/R₁ + 1/R₂ + ...
串联电路：各处电流相等；总电阻 Rₜ = R₁ + R₂ + ... ；各电压相加。并联电路：各支路两端电压相等；总电流为各支路电流之和；1/Rₜ = 1/R₁ + 1/R₂ + ...
esistivity ρ: R = ρ l / A. A variable resistor (rheostat) can change current in a circuit.
电阻取决于长度 l、横截面积 A 和材料电阻率 ρ：R = ρ l / A。可变电阻（变阻器）可改变电路中的电流。
11. Electromagnetism | 电磁学
A magnetic field exists around a magnet or a current-carrying conductor. Field lines go from N to S pole. An electromagnet is made by coiling a wire around a soft iron core; its strength increases with more current or more turns.
磁铁或载流导体周围存在磁场。磁感线从 N 极指向 S 极。将导线绕在软铁心上可制成电磁铁；增大电流或增加匝数可增强其磁性。
A current-carrying wire in a magnetic field experiences a force (motor effect). Fleming' = B I L, where B is magnetic flux density, I is current, L is length of wire in the field.
置于磁场中的载流导线会受到力的作用（电动机效应）。弗莱明左手定则给出力的方向。力 F = B I L，B 为磁通量密度，I 为电流，L 为导线在磁场中的长度。
Electromagnetic induction: when a conductor moves relative to a magnetic field or the field changes, an e.m.f. is induced. The generator effect produces alternating current if the coil rotates continuously.
电磁感应：当导体相对磁场运动或磁场发生变化时，会感应出电动势。若线圈持续旋转，发电机效应产生交流电。
formers increase voltage and decrease current, reducing energy loss in transmission lines.
变压器可改变交流电压：Vₚ / Vₛ = nₚ / nₛ（理想变压器）。输入功率 ≈ 输出功率：Iₚ Vₚ = Iₛ Vₛ。升压变压器升高电压、减小电流，从而减少输电线路能量损耗。
12. Atomic and Space Physics | 原子与空间物理
r (atomic number) Z determines the element; nucleon number (mass number) A = Z + neutrons.
具有核式结构的原子有一个带正电的微小原子核，内有质子和中子，核外电子分层排列。质子数（原子序数）Z 决定元素种类；核子数（质量数）A = Z + 中子数。
Isotopes are atoms of the same element with different numbers of neutrons. Radionuclides emit alpha (α), beta (β), or gamma (γ) radiation. Alpha is a helium nucleus, beta is a high-speed electron, gamma is an electromagnetic wave.
同位素是质子数相同而中子数不同的同种原子。放射性核素会放出 α、β 或 γ 辐射。α 是氦核，β 是高速电子，γ 是电磁波。
Radioactive decay is random. Half-life t½ is the time for half the nuclei in a sample to decay. Background radiation comes from natural sources and is always present.
放射性衰变是随机的。半衰期 t½ 是样品中半数原子核发生衰变所需的时间。本底辐射来自天然源，始终存在。
Nuclear fission is the splitting of a large nucleus (e.g., uranium-235) into smaller parts,
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