AS AQA Physics Unit 1: Particles and Quantum Phenomena — AQA AS物理第一单元：粒子与量子现象

一、原子结构与同位素：原子核的组成 | Atomic Structure and Isotopes: Inside the Nucleus

AS物理第一单元从原子的基本结构开始。一个原子由位于中心的原子核和围绕它运动的电子组成。原子核又由两种粒子构成：质子和中子。质子带一个单位正电荷，电荷量为 +1.60×10⁻¹⁹ 库仑，质量约为 1.67×10⁻²⁷ 千克；中子不带电，质量与质子几乎相同；电子带一个单位负电荷，电荷量为 -1.60×10⁻¹⁹ 库仑，但质量仅为质子的约 1/1800，约为 9.11×10⁻³¹ 千克。理解这些基本数值是解答选择题和计算题的第一步。

Unit 1 of AS Physics begins with the basic structure of the atom. An atom consists of a central nucleus surrounded by orbiting electrons. The nucleus itself is made of two kinds of particle: protons and neutrons. A proton carries a single positive charge of +1.60×10⁻¹⁹ coulombs and a mass of about 1.67×10⁻²⁷ kg; a neutron carries no charge and has almost the same mass as the proton; an electron carries a single negative charge of -1.60×10⁻¹⁹ coulombs but a mass of only about 1/1800 of the proton, roughly 9.11×10⁻³¹ kg. Knowing these fundamental values is the first step to answering both multiple-choice and calculation questions.

考试中频繁出现的一个概念是”比荷”（specific charge），它定义为粒子的电荷量与其质量的比值，单位是 C kg⁻¹。质子的比荷约为 9.58×10⁷ C kg⁻¹，而电子的比荷约为 1.76×10¹¹ C kg⁻¹，大约比质子大 1800 倍，因为两者电荷量大小相同而电子质量小得多。比荷的计算通常要求先根据质量数和原子序数确定质子数和中子数，再对原子核整体进行计算。

A concept that appears frequently in exams is specific charge, defined as the ratio of a particle’s charge to its mass, measured in C kg⁻¹. The specific charge of a proton is about 9.58×10⁷ C kg⁻¹, while that of an electron is about 1.76×10¹¹ C kg⁻¹, roughly 1800 times larger because the two have equal charge but the electron is far less massive. Calculations of specific charge usually require you to first work out the number of protons and neutrons from the mass number and atomic number, then apply the calculation to the whole nucleus.

同位素（isotopes）是质子数相同但中子数不同的同一种元素的不同形式。它们的化学性质相同，但质量数不同。在题目中，你会看到用符号 AZX 表示原子核，其中 A 是质量数（质子数加中子数），Z 是原子序数（质子数）。例如碳-12 和碳-14 都是碳的同位素，分别含有 6 个和 8 个中子。

Isotopes are different forms of the same element that have the same number of protons but different numbers of neutrons. They are chemically identical but have different mass numbers. In exam questions you will see nuclei represented using the notation AZX, where A is the mass number (protons plus neutrons) and Z is the atomic number (protons). For example, carbon-12 and carbon-14 are both isotopes of carbon, containing 6 and 8 neutrons respectively.

二、四种基本力与粒子分类：强子与轻子 | Fundamental Forces and Particle Classification: Hadrons vs Leptons

粒子物理学用四种基本相互作用来解释宇宙中所有力的现象：强核力、电磁力、弱核力和引力。强核力把原子核内的质子和中子束缚在一起，克服质子之间巨大的静电排斥力，它的作用范围极短，仅约 10⁻¹⁵ 米，但在这个距离内它是最强的力。弱核力负责贝塔衰变等过程，引力在粒子尺度上最弱，通常可以忽略。

Particle physics explains all force phenomena in the universe using four fundamental interactions: the strong nuclear force, the electromagnetic force, the weak nuclear force and gravity. The strong nuclear force binds protons and neutrons together inside the nucleus, overcoming the enormous electrostatic repulsion between protons; its range is extremely short, only about 10⁻¹⁵ m, but within that distance it is the strongest force. The weak nuclear force is responsible for processes such as beta decay, while gravity is the weakest at the particle scale and can usually be ignored.

根据是否参与强相互作用，粒子被分为两大类：强子（hadrons）和轻子（leptons）。强子会感受到强核力，又分为重子（baryons）和介子（mesons）。质子、中子都是重子，由三个夸克组成；介子如π介子和K介子由一个夸克和一个反夸克组成。轻子不参与强相互作用，包括电子、μ子以及与之对应的中微子。记住这个分类树是解决”粒子属于哪一类”题目的关键。

Particles are divided into two broad groups according to whether they take part in the strong interaction: hadrons and leptons. Hadrons feel the strong nuclear force and are further divided into baryons and mesons. Protons and neutrons are baryons, made of three quarks, while mesons such as pions and kaons are made of one quark and one antiquark. Leptons do not participate in the strong interaction and include the electron, the muon and their associated neutrinos. Remembering this classification tree is the key to answering “which type of particle is this” questions.

在分析粒子反应时，守恒定律是判断一个反应能否发生的最有力工具。电荷守恒、重子数守恒和轻子数守恒都必须满足。每个轻子带轻子数 +1，每个反轻子带轻子数 -1，反应前后轻子数必须相等。AQA的题目经常要求你检查一个给定的衰变方程是否满足这些守恒律，并据此判断它是否可能发生。

When analysing particle reactions, conservation laws are the most powerful tool for deciding whether a reaction can occur. Charge, baryon number and lepton number must all be conserved. Each lepton carries lepton number +1 and each antilepton carries -1, and the total lepton number must be equal before and after the reaction. AQA questions frequently ask you to check whether a given decay equation satisfies these conservation laws and to use them to decide whether the process is possible.

三、夸克与强子的组成：质子与中子的夸克模型 | Quarks and the Composition of Hadrons: The Quark Model of Proton and Neutron

夸克是构成强子的基本粒子。AS考试大纲主要涉及三种夸克：上夸克（up，电荷 +2/3 e）、下夸克（down，电荷 -1/3 e）和奇异夸克（strange，电荷 -1/3 e）。质子由两个上夸克和一个下夸克（uud）组成，其电荷为 +2/3 + 2/3 – 1/3 = +1 e，恰好等于质子带的一个单位正电荷。中子由两个下夸克和一个上夸克（udd）组成，电荷为 -1/3 – 1/3 + 2/3 = 0，解释了中子为什么呈电中性。

Quarks are the fundamental particles that make up hadrons. The AS specification mainly involves three quarks: the up quark (charge +2/3 e), the down quark (charge -1/3 e) and the strange quark (charge -1/3 e). The proton is made of two up quarks and one down quark (uud), giving a total charge of +2/3 + 2/3 – 1/3 = +1 e, exactly the single positive charge carried by the proton. The neutron is made of two down quarks and one up quark (udd), giving a charge of -1/3 – 1/3 + 2/3 = 0, which explains why the neutron is electrically neutral.

每一个夸克都有一个对应的反夸克，电荷符号相反。反上夸克电荷为 -2/3 e，反下夸克电荷为 +1/3 e。介子由夸克和反夸克组成，例如π⁺介子由上夸克和反下夸克组成（u d̄），电荷为 +2/3 + 1/3 = +1 e。能够用夸克组合推导出粒子的电荷和重子数，是这一单元的核心技能。

Every quark has a corresponding antiquark with the opposite charge. The anti-up quark has charge -2/3 e and the anti-down quark has charge +1/3 e. Mesons are made of a quark and an antiquark; for example, the π⁺ meson is made of an up quark and an anti-down quark (u d̄), giving a charge of +2/3 + 1/3 = +1 e. Being able to derive a particle’s charge and baryon number from its quark composition is a core skill in this unit.

奇异数（strangeness）是奇异夸克引入的一个量子数。奇异粒子（含奇异夸克）总是成对产生，因为强相互作用过程必须保持奇异数守恒，而在弱相互作用衰变中奇异数可以不守恒，因此奇异粒子的衰变相对较慢。题目中如果出现K介子或其他含奇异夸克的粒子，通常需要你在反应方程中追踪奇异数的变化。

Strangeness is a quantum number introduced by the strange quark. Strange particles (those containing strange quarks) are always produced in pairs, because strong interaction processes must conserve strangeness, whereas in weak interaction decays strangeness need not be conserved, so strange particles decay relatively slowly. If a kaon or another particle containing strange quarks appears in a question, you will usually need to track how strangeness changes across the reaction equation.

四、反物质与湮灭：能量与质量的相互转化 | Antimatter, Annihilation and Pair Production: Converting Energy and Mass

每一种粒子都有一个对应的反粒子（antiparticle），其质量相同但电荷和某些量子数相反。电子的反粒子是正电子（positron），带正电；质子的反粒子是反质子，带负电。有些中性粒子（如光子）的反粒子就是它本身。反物质并不是科幻概念，它在实验室和医学（如正电子发射断层扫描 PET）中都有真实应用。

Every particle has a corresponding antiparticle with the same mass but opposite charge and certain opposite quantum numbers. The antiparticle of the electron is the positron, which is positively charged; the antiparticle of the proton is the antiproton, which is negatively charged. Some neutral particles, such as the photon, are their own antiparticles. Antimatter is not science fiction; it has real applications in laboratories and in medicine, for example in positron emission tomography (PET) scans.

湮灭（annihilation）发生在粒子与其反粒子相遇时，两者互相抵消，质量全部转化为能量，以两个光子（或一对γ射线）的形式释放。根据爱因斯坦的质能方程 E = mc²，释放的总能量等于两个粒子的静止质量能量之和。湮灭过程必须同时满足动量和能量守恒，因此通常产生两个沿相反方向运动的光子。

Annihilation occurs when a particle meets its antiparticle: the two cancel each other out and all their mass is converted into energy, released in the form of two photons (or a pair of gamma rays). According to Einstein’s mass-energy equation E = mc², the total energy released equals the sum of the rest-mass energies of the two particles. Annihilation must conserve both momentum and energy, which is why it usually produces two photons moving in opposite directions.

与湮灭相反的过程是电子对产生（pair production）。当一个高能光子（能量至少等于两个粒子的静止质量能量 2mc²）从原子核附近经过时，它可以转化为一个粒子和一个反粒子对，例如一个电子和一个正电子。多余的能量转化为粒子对的动能。湮灭把质量变成能量，电子对产生把能量变成质量，两者是理解”质量与能量等价”这一思想的最佳例证。

The reverse process of annihilation is pair production. When a high-energy photon (with energy at least equal to the rest-mass energy of two particles, 2mc²) passes near a nucleus, it can be converted into a particle-antiparticle pair, such as an electron and a positron. Any surplus energy becomes the kinetic energy of the pair. Annihilation turns mass into energy, while pair production turns energy into mass, and together they are the best illustrations of the idea that mass and energy are equivalent.

五、光子与电磁辐射：光是一份一份的能量 | The Photon Model and Electromagnetic Radiation: Light as Packets of Energy

经典波动理论把电磁辐射看作连续的波，但量子物理告诉我们，电磁辐射的能量是量子化的，以不连续的”光子”（photon）为单位传递。一个光子的能量只取决于它的频率，用公式 E = hf 表示，其中 h 是普朗克常数，约等于 6.63×10⁻³⁴ J s。由于频率与波长的关系 f = c/λ，光子能量也可以写成 E = hc/λ。

Classical wave theory treats electromagnetic radiation as a continuous wave, but quantum physics tells us that the energy of electromagnetic radiation is quantised, delivered in discrete packets called photons. The energy of a photon depends only on its frequency, given by the formula E = hf, where h is Planck’s constant, approximately 6.63×10⁻³⁴ J s. Since frequency and wavelength are related by f = c/λ, the photon energy can also be written as E = hc/λ.

理解”光子能量只与频率有关”这一点非常重要。频率越高（波长越短），单个光子携带的能量越大。这就是为什么紫外线光子能导致晒伤，而同样强度的无线电波光子能量极低，完全无害。考试中经常要求你比较不同颜色光或不同频段电磁波的光子能量，或用 E = hf 和 E = hc/λ 做单位换算和数值计算。

Understanding that photon energy depends only on frequency is very important. The higher the frequency (the shorter the wavelength), the greater the energy carried by a single photon. This is why ultraviolet photons can cause sunburn, whereas radio-wave photons of the same intensity carry far too little energy to cause harm. Exams often ask you to compare the photon energies of different colours of light or different bands of the electromagnetic spectrum, or to perform unit conversions and numerical calculations using E = hf and E = hc/λ.

在进行计算时，能量的单位换算是一个常见的失分点。光子能量通常用焦耳（J）表示，但粒子物理中也常用电子伏特（eV）：1 eV = 1.60×10⁻¹⁹ J。当题目给出波长（单位 nm）时，记得先换算成米，再代入 E = hc/λ。仔细处理科学计数法和单位，能让你在计算题中稳拿分数。

When performing calculations, unit conversion is a common place to lose marks. Photon energy is usually expressed in joules (J), but particle physics also uses electronvolts (eV): 1 eV = 1.60×10⁻¹⁹ J. When a question gives a wavelength in nanometres, remember to convert it to metres before substituting into E = hc/λ. Handling scientific notation and units carefully will let you score reliably on calculation questions.

六、光电效应：光的粒子性的决定性证据 | The Photoelectric Effect: Decisive Evidence for the Particle Nature of Light

光电效应是指当一束频率足够高的光照射到金属表面时，金属会发射出电子的现象。这个现象有三个无法用波动理论解释的特征：第一，只有当光的频率超过某个临界值（称为截止频率 threshold frequency）时才会发射电子，低于这个频率，无论光有多强，都不会发射电子；第二，电子几乎是瞬间发射的，没有时间延迟；第三，增大光强只会增加发射电子的数量，不会改变单个电子的最大动能。

The photoelectric effect is the emission of electrons from a metal surface when light of a sufficiently high frequency shines on it. This phenomenon has three features that wave theory cannot explain. First, electrons are only emitted when the light’s frequency exceeds a critical value called the threshold frequency; below this frequency, no electrons are emitted no matter how intense the light is. Second, the electrons are emitted almost instantly, with no time delay. Third, increasing the intensity only increases the number of electrons emitted, not the maximum kinetic energy of each electron.

爱因斯坦用光子模型完美解释了这些观察结果。他认为每个电子只能吸收一个光子的能量。金属中的电子要逃离表面，需要克服一个最小能量，称为逸出功（work function）Φ，它等于截止频率乘以普朗克常数：Φ = hf₀。如果一个光子的能量大于逸出功，电子就会以最大动能 Ek = hf – Φ 发射出去，这就是著名的爱因斯坦光电方程 hf = Φ + Ek(max)。

Einstein explained these observations perfectly using the photon model. He proposed that each electron absorbs the energy of exactly one photon. To escape the metal surface, an electron must overcome a minimum energy called the work function Φ, which equals the threshold frequency multiplied by Planck’s constant: Φ = hf₀. If a photon’s energy is greater than the work function, the electron is emitted with a maximum kinetic energy Ek = hf – Φ. This is the famous Einstein photoelectric equation hf = Φ + Ek(max).

光电效应是”光具有粒子性”的决定性证据。波动理论预测，只要光照射足够长时间，电子就能积累足够能量逃逸，并且光越强电子能量越大，但实验证明事实并非如此。光子模型则一步到位地解释了截止频率、瞬时发射和光强只影响电子数量等现象。AQA的题目经常要求你用光电效应解释为什么光必须被看作粒子，或根据 Ek 对 f 的图像求出逸出功和普朗克常数。

The photoelectric effect is decisive evidence that light behaves as particles. Wave theory predicts that as long as light shines for long enough, electrons could accumulate enough energy to escape, and that brighter light should give electrons more energy, but experiment shows this is not the case. The photon model, by contrast, explains the threshold frequency, the instantaneous emission and the fact that intensity only affects electron number in one step. AQA questions often ask you to use the photoelectric effect to explain why light must be treated as particles, or to find the work function and Planck’s constant from a graph of Ek against f.

七、能级与原子光谱：电子为什么只能待在特定的轨道 | Energy Levels and Atomic Spectra: Why Electrons Occupy Only Certain States

原子中的电子不能拥有任意的能量，只能处于一系列分立的能级（energy levels）上。最低的能级叫基态（ground state），高于基态的能级叫激发态（excited states）。电子要从一个能级跃迁到更高的能级，必须恰好吸收一个能量等于两个能级能量差的光子；如果光子的能量不对，电子就不会发生跃迁。这就是为什么原子只会吸收特定频率的光。

Electrons in an atom cannot have arbitrary energy; they can only occupy a series of discrete energy levels. The lowest level is called the ground state, and levels above it are called excited states. For an electron to jump to a higher level, it must absorb a photon whose energy exactly equals the difference between the two levels; if the photon energy does not match, the transition does not happen. This is why atoms only absorb light of specific frequencies.

如果光子能量足够大，电子可以被完全移出原子，这个过程叫电离（ionisation），所需的最小能量叫电离能。当处于激发态的电子回落到较低的能级时，会释放出一个光子，其能量等于两个能级之差：hf = E₁ – E₂。因为能级是分立的，发射出来的光子也只有特定的频率，这就解释了为什么每种元素都有自己独特的线状光谱（line spectrum），就像指纹一样可以用来识别元素。

If the photon energy is large enough, the electron can be removed from the atom entirely; this process is called ionisation, and the minimum energy required is the ionisation energy. When an excited electron falls back to a lower level, it releases a photon whose energy equals the difference between the two levels: hf = E₁ – E₂. Because the levels are discrete, the emitted photons only have specific frequencies, which explains why each element has its own unique line spectrum that, like a fingerprint, can be used to identify the element.

荧光灯管是能级概念的经典应用。灯管内的汞原子被电子撞击激发后，会发射紫外光子；这些紫外光子撞击管壁的荧光涂层，使涂层中的电子跃迁到激发态，再回落到较低能级时发射出可见光。整个过程是”吸收特定能量光子、发射不同频率光子”的连续链条。这类题目考察你对能级跃迁和光子能量关系的理解。

The fluorescent tube is a classic application of the energy-level concept. Inside the tube, mercury atoms are excited by collisions with electrons and then emit ultraviolet photons; these UV photons strike the fluorescent coating on the tube wall, exciting the coating’s electrons, which then emit visible light as they fall back to lower levels. The whole process is a continuous chain of absorbing photons of one energy and emitting photons of different frequencies. Questions like this test your understanding of the relationship between energy-level transitions and photon energy.

八、波粒二象性：物质也有波动性 | Wave-Particle Duality: Matter Also Behaves as a Wave

光既能表现出波动性（如衍射和干涉），也能表现出粒子性（如光电效应），这种现象称为波粒二象性。德布罗意（de Broglie）大胆地提出，这种二象性不仅适用于光，也适用于所有物质粒子。他给出一个粒子的德布罗意波长公式：λ = h/p = h/mv，其中 p 是粒子的动量。动量越大，波长越短。

Light can behave both as a wave (as in diffraction and interference) and as a particle (as in the photoelectric effect), a phenomenon called wave-particle duality. De Broglie boldly proposed that this duality applies not only to light but to all matter particles as well. He gave the de Broglie wavelength of a particle as λ = h/p = h/mv, where p is the particle’s momentum. The greater the momentum, the shorter the wavelength.

电子衍射实验为物质的波动性提供了确凿证据。当一束电子通过石墨薄膜或金属晶格时，会产生与光波类似的衍射环，说明运动的电子确实表现得像波。电子的德布罗意波长通常只有纳米级或更小，因此只有穿过原子尺度的结构时才能观察到衍射。这个实验证明了物质粒子具有波动性，也奠定了电子显微镜的工作原理。

Electron diffraction experiments provide decisive evidence for the wave nature of matter. When a beam of electrons passes through a thin graphite film or a metal lattice, it produces diffraction rings similar to those of light waves, showing that moving electrons really do behave like waves. The de Broglie wavelength of an electron is typically only nanometres or less, so diffraction can only be observed when it passes through structures on the atomic scale. This experiment proves that matter particles have wave properties and underpins the working principle of the electron microscope.

在计算题中，德布罗意波长公式常与动能结合使用。由于动能 Ek = p²/2m，可以推导出 p = √(2mEk)，进而用 λ = h/√(2mEk) 求出波长。题目可能要求你比较质子和电子在相同动能下的波长：因为质子质量大，其动量更大，波长更短。掌握”动量越大、波长越短”这条核心结论，就能快速判断比较类问题。

In calculation questions, the de Broglie wavelength formula is often combined with kinetic energy. Since kinetic energy Ek = p²/2m, we can derive p = √(2mEk) and then use λ = h/√(2mEk) to find the wavelength. A question might ask you to compare the wavelengths of a proton and an electron with the same kinetic energy: because the proton is more massive, it has greater momentum and therefore a shorter wavelength. Mastering the core conclusion “greater momentum means shorter wavelength” lets you quickly resolve comparison questions.

九、考试技巧：AS物理第一单元的解题框架 | Exam Technique: A Framework for AS Physics Unit 1 Questions

AQA的AS物理第一单元考试以选择题和简答题为主，答题的关键在于”定义准确、公式清晰、单位正确”。首先，务必熟记基本粒子的性质表：质子、中子、电子的电荷与质量，以及上、下、奇异夸克的电荷。其次，把守恒定律（电荷、重子数、轻子数、奇异数）当作检查每个粒子反应方程的第一步，这能帮你快速排除不可能的选项。

The AQA AS Physics Unit 1 exam consists mainly of multiple-choice and short-answer questions, and the key to success is “accurate definitions, clear formulas and correct units”. First, memorise the property table of fundamental particles: the charges and masses of the proton, neutron and electron, plus the charges of the up, down and strange quarks. Second, treat the conservation laws (charge, baryon number, lepton number, strangeness) as your first check on every particle reaction equation; this lets you quickly eliminate impossible options.

在计算题中，最常见的失分原因是单位混乱。光子能量 E = hf 通常给出以焦耳为单位的答案，但逸出功和电离能可能以电子伏特给出，此时必须用 1 eV = 1.60×10⁻¹⁹ J 进行换算。波长给出 nm 时要换算成 m 再代入 E = hc/λ。比荷的计算要先正确数出核内的质子和中子数。把这些换算步骤写清楚，即使最终结果算错，也能保住大部分过程分。

In calculation questions, the most common cause of lost marks is confused units. The photon energy E = hf normally gives an answer in joules, but the work function and ionisation energy may be given in electronvolts, in which case you must convert using 1 eV = 1.60×10⁻¹⁹ J. When a wavelength is given in nm, convert it to metres before using E = hc/λ. For specific charge, count the protons and neutrons in the nucleus correctly first. Writing out these conversion steps clearly preserves most of the method marks even if the final answer is wrong.

图像题是这一单元的高频考点。光电效应的 Ek 对 f 图像是一条斜率为普朗克常数 h、与频率轴交于截止频率 f₀ 的直线，截距的绝对值为逸出功 Φ。做题时，先写出爱因斯坦方程 hf = Φ + Ek(max)，把它整理成 y = mx + c 的形式，再对照图像读取斜率、截距和交点，问题就迎刃而解。清晰的物理图像加熟练的公式变形，是拿下高分的不二法门。

Graph questions are a high-frequency feature of this unit. The graph of Ek against f for the photoelectric effect is a straight line whose gradient is Planck’s constant h and whose intercept on the frequency axis is the threshold frequency f₀, with the magnitude of the intercept equal to the work function Φ. When tackling these questions, first write out Einstein’s equation hf = Φ + Ek(max), rearrange it into the form y = mx + c, then read the gradient, intercept and intersection from the graph, and the problem is solved. A clear physical picture plus fluent formula rearrangement is the surest route to high marks.

Summary | 总结

AS物理第一单元以”量子化”这一思想贯穿始终：能量以光子的形式一份一份地传递，原子中的电子只能占据分立的能级，物质粒子本身也具有波动性。从原子核的组成，到夸克与轻子的分类，再到反物质、光电效应和波粒二象性，这一单元建立起了现代物理的基本图景，是后续学习电学、力学和更深入量子物理的基础。

AS Physics Unit 1 is held together by a single idea, quantisation: energy is delivered in discrete packets called photons, electrons in an atom can only occupy discrete energy levels, and matter particles themselves behave as waves. From the composition of the nucleus, through the classification of quarks and leptons, to antimatter, the photoelectric effect and wave-particle duality, this unit builds up the fundamental picture of modern physics and lays the foundation for later study of electricity, mechanics and deeper quantum physics.

掌握本单元的关键在于三点：熟记基本粒子的电荷、质量与夸克组成；熟练运用守恒定律判断粒子反应；以及能够用 E = hf、hf = Φ + Ek(max) 和 λ = h/p 三个核心公式解决计算题和图像题。只要把定义记牢、单位换算做对、公式变形熟练，这一单元的分数并不难拿。祝愿每一位考生在考试中取得理想的成绩。

The key to mastering this unit lies in three things: memorising the charges, masses and quark compositions of the fundamental particles; using the conservation laws fluently to judge particle reactions; and being able to solve calculation and graph questions with the three core formulas E = hf, hf = Φ + Ek(max) and λ = h/p. As long as you remember the definitions, get the unit conversions right and rearrange formulas fluently, the marks in this unit are not hard to earn. Best wishes to every candidate for excellent results.

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