📚 WJEC Year 13 Physics: High-Frequency Terminology Memory Guide | WJEC 十三年级物理：高频术语速记指南
Nailing the vocabulary in WJEC Year 13 Physics is not just about reciting definitions – it’s about unlocking the equations and recognising the patterns that examiners love. This rapid-fire guide walks you through the essential terms from oscillations, nuclei, fields, capacitance, electromagnetism and popular options, complete with mnemonics and bite-sized reminders that will stick in your long-term memory.
攻克 WJEC 十三年级物理的词汇不仅仅是背诵定义，更能帮你理清公式、看透考官常设的模式。这份速记指南带你快速掌握振动、核物理、场、电容、电磁学和热门选考模块的核心术语，附上朗朗上口的记忆口诀和简短醒目的提醒，让考点牢牢印在你的长期记忆中。
1. SHM & Oscillations | 简谐运动与振动
Simple harmonic motion is the heartbeat of Year 13 physics. A neat acronym is ‘PADAV’: Period, Amplitude, Displacement, Angular frequency, Velocity, Acceleration. Everything orbits around the sinusoidal equation x = A sin(ωt + φ).
简谐运动是十三年级物理的心跳。一个便利的首字母组是“PADAV”：周期、振幅、位移、角频率、速度、加速度。一切都围绕着正弦方程 x = A sin(ωt + φ) 旋转。
Displacement x is measured from the equilibrium position; the restoring force always points backwards. For a spring, F = -kx, where k is the spring constant in N m⁻¹ – the stiffer the spring, the higher k.
位移 x 从平衡位置测量；恢复力始终指向回正。对弹簧，F = -kx，其中 k 是劲度系数，单位 N m⁻¹ ——弹簧越硬，k 值越大。
Angular frequency ω = 2πf = 2π/T (unit rad s⁻¹). It sets the pace of oscillation. The hallmark differential equation is d²x/dt² = -ω²x – whenever you spot this form, SHM is on the cards.
角频率 ω = 2πf = 2π/T（单位 rad s⁻¹），决定着振动的快慢。标志性微分方程是 d²x/dt² = -ω²x ——一旦遇到这个形式，简谐运动就登场了。
Phase difference φ (in radians) keeps track of leads and lags. In SHM, velocity leads displacement by π/2, acceleration leads displacement by π and is always opposite to it. The classic energy swap between Ek and Ep totals ½kA².
相位差 φ（弧度）指示超前与滞后。在简谐运动中，速度超前位移 π/2，加速度超前位移 π并始终与位移反向。动能和势能之间经典的交替总和为 ½kA²。
Resonance occurs when the driving frequency matches the natural frequency; the amplitude becomes huge and the curve’s sharpness is governed by damping – light damping gives a tall, narrow peak.
共振发生在驱动力频率与固有频率匹配时；振幅变得巨大，曲线的尖锐程度取决于阻尼——轻阻尼产生高而窄的峰值。
2. Waves & Superposition | 波与叠加
Wave vocabulary trips up many students because they confuse transverse (light, water) and longitudinal (sound, P-waves). Lock in that transverse waves can be polarised; longitudinal waves cannot.
波的词汇常让学生混淆：横波（光、水波）和纵波（声波、P波）必须分清。牢记横波可以偏振，纵波不能。
Path difference is the extra distance travelled by one wave relative to another, measured in wavelengths or metres. Constructive interference happens when path difference = nλ; destructive when path difference = (n + ½)λ.
路程差是指一个波比另一个多走的距离，以波长或米度量。当路程差 = nλ 时产生相长干涉；路程差 = (n + ½)λ 时产生相消干涉。
Coherence is the secret sauce for stable interference patterns – waves must have the same frequency and a constant phase difference. Lasers are the textbook coherent source.
相干性是稳定干涉图样的秘诀——波必须具有相同频率且恒定的相位差。激光就是教科书式的相干光源。
Young’s double-slit fringe spacing: Δy = λD / d. Here D is the slit-to-screen distance and d the slit separation. A smaller d spreads the fringes wider. For a diffraction grating, the bright orders obey d sin θ = nλ.
杨氏双缝干涉条纹间距：Δy = λD / d。其中 D 是双缝到屏的距离，d 是缝间距。缝间距越小，条纹展得越宽。对于衍射光栅，亮纹满足 d sin θ = nλ。
Diffraction is the spreading of a wave around an obstacle or slit. It is most pronounced when the gap size is comparable to the wavelength – this is why long radio waves diffract around hills.
衍射是波绕障碍物或通过狭缝时的弯曲。当缝隙尺寸与波长相近时衍射最明显——这就是为什么长波无线电能绕山传播。
3. Nuclear & Radiation | 核物理与辐射
The nuclear section bombards you with decay terms. Activity A = λN, the number of decays per second (becquerel, Bq). The decay constant λ is the probability per unit time that a nucleus will decay.
核物理部分用衰变术语不断“轰击”你。活度 A = λN，为每秒衰变次数（贝可勒尔，Bq）。衰变常数 λ 是每个原子核在单位时间内衰变的概率。
Half-life T½ = ln2 / λ – this is the time for half the nuclei to decay. After one half-life, activity and count rate also halve. The exponential decay law is N = N₀ e^{-λt}.
半衰期 T½ = ln2 / λ ——这是半数原子核衰变所需的时间。一个半衰期后，活度和计数率也减半。指数衰变规律为 N = N₀ e^{-λt}。
Mass defect and binding energy: the mass of a nucleus is less than the sum of its separate nucleons. This ‘missing mass’ Δm appears as the binding energy E = Δm c². A common unit is 1 u = 931.5 MeV – memorise this number!
质量亏损与结合能：原子核的质量比其独立核子质量之和略小。这些“丢失的质量” Δm 转化为结合能 E = Δm c²。常用换算 1 u = 931.5 MeV ——必须记住这个数字！
Fission is splitting a heavy nucleus (e.g. uranium-235) into two lighter fragments, releasing neutrons. Fusion is joining light nuclei (like deuterium and tritium) to form helium, releasing even more energy per mass. Chain reactions rely on slow neutrons, controlled by moderators (water, graphite).
裂变是将重核（如铀-235）分裂成两个较轻碎片并释放中子。聚变是轻核（如氘和氚）结合形成氦，单位质量释放的能量更大。链式反应依赖慢中子，并由慢化剂（水、石墨）控制。
4. Gravitational & Electric Fields | 引力场与电场
Fields are invisible but follow simple inverse-square patterns. Gravitational field strength g = F/m, and for a point mass g = GM/r². Electric field strength E = F/q; for a point charge E = Q/(4πε₀r²).
场虽看不见，却遵循简单的平方反比规律。引力场强度 g = F/m，对点质量有 g = GM/r²。电场强度 E = F/q；对点电荷有 E = Q/(4πε₀r²)。
Potential is energy per unit mass/charge: gravitational potential Vg = -GM/r (always negative, rising to zero at infinity); electric potential V = Q/(4πε₀r). Equipotential surfaces are always perpendicular to field lines.
势能（位）是单位质量或电荷的能量：引力势 Vg = -GM/r（恒为负值，至无穷远处趋近于零）；电势 V = Q/(4πε₀r)。等势面始终与电场线垂直。
In a uniform electric field between two parallel plates, E = V/d (V m⁻¹). Electrons accelerated through a potential difference V gain kinetic energy eV = ½mv².
在两块平行板间的匀强电场中，E = V/d（V m⁻¹）。电子经过电势差 V 加速后获得的动能 eV = ½mv²。
Remember Coulomb’s law: F = 1/(4πε₀) × Q₁Q₂/r². The permittivity of free space ε₀ = 8.85 × 10⁻¹² F m⁻¹. WJEC often asks about the similarities and differences between gravitational and electric fields – both are inverse-square but gravitational force is always attractive and much weaker.
记住库仑定律：F = 1/(4πε₀) × Q₁Q₂/r²。真空电容率 ε₀ = 8.85 × 10⁻¹² F m⁻¹。WJEC 常要求比较引力场和电场的异同——两者皆满足平方反比关系，但引力总是吸引力且极其微弱。
5. Capacitance & Dielectrics | 电容与电介质
Capacitance C = Q/V measures how much charge a capacitor stores per volt (farad, F). A capacitor stores energy in its electric field; the three equivalent forms are U = ½QV = ½CV² = ½Q²/C.
电容 C = Q/V 衡量每伏特电压下电容器储存的电荷量（法拉，F）。电容器在电场中储存能量；三个等效表达为 U = ½QV = ½CV² = ½Q²/C。
The time constant τ = RC tells you how fast a capacitor charges or discharges. After one τ, the voltage has fallen to 37% of its initial value. Exponential charging: V = V₀(1 – e^{-t/RC}); discharging: V = V₀ e^{-t/RC}.
时间常数 τ = RC 指示电容充放电的快慢。一个时间常数后，电压降至初始值的 37%。指数充电：V = V₀(1 – e^{-t/RC})；放电：V = V₀ e^{-t/RC}。
Adding a dielectric between the plates increases capacitance by the relative permittivity εr (also called dielectric constant). The new capacitance becomes C = ε₀εr A / d. Polar molecules in the dielectric reduce the effective field.
在极板间加入电介质可将电容增加相对电容率 εr（又称介电常数）倍。新电容为 C = ε₀εr A / d。介质中的极性分子削弱了有效电场。
Combining capacitors: parallel → Ctotal = C₁ + C₂ (like increasing plate area); series → 1/Ctotal = 1/C₁ + 1/C₂ (like increasing plate separation).
电容器组合：并联 → C总 = C₁ + C₂（如同增大极板面积）；串联 → 1/C总 = 1/C₁ + 1/C₂（如同增大极板间距）。
6. Magnetic Fields & Induction | 磁场与电磁感应
Magnetic flux density B (tesla, T) describes the strength of a magnetic field. Magnetic flux Φ = BA cos θ, where θ is the angle between the field lines and the normal to the area. A change in flux induces an emf – Faraday’s law: ε = -N dΦ/dt.
磁通量密度 B（特斯拉，T）描述磁场的强度。磁通量 Φ = BA cos θ，其中 θ
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