China 高三 Physics

1. Selective 3 Ch.1 Molecular kinetic theory

Basic ideas; oil-film estimate of molecule size · Speed distribution; molecular KE and PE

• Kinetic Theory of Gases: Pressure, Temperature and rms Speed – Kinetic theory explains gas behaviour by picturing a gas as tiny, fast, randomly moving molecules that bounce elastically and do not pull on each other. Each hit on a wall reverses the molecule's velocity and hands the wall momentum 2mvₓ. Adding the hits of all molecules gives the pressure P = ⅓ n m v̄² = ⅓ ρ v̄². Comparing with PV = N k T shows that the average kinetic energy of a molecule is (3/2) k T: temperature is a measure of the average kinetic energy of the molecules. The root mean square speed is v_rms = √(3RT/M) = √(3kT/m), so lighter gases move faster at the same temperature.

2. Selective 3 Ch.2 Gases, solids, liquids

Temperature scales; gas laws; ideal gas · Crystals and amorphous solids; liquid crystals · Surface tension; capillarity

• Perfect Gas Equation PV = nRT and Work in Compressing a Gas – A gas is made of countless tiny molecules flying about. Their hits on the walls make pressure. For a low-density gas, three simple laws hold: at fixed temperature, P × V stays constant (Boyle); at fixed pressure, V grows in step with kelvin temperature (Charles); at the same P and T, equal volumes hold equal numbers of molecules (Avogadro). Put together they give the perfect gas equation PV = nRT = N k T. One mole holds Avogadro's number, 6.022 × 10²³, of particles. Pushing a piston in does work on the gas; the work equals the area under the P–V graph, and at fixed temperature W = nRT ln(V₁/V₂).
• The Solid State – In a solid the particles sit close together and only vibrate in place, so a solid keeps its shape. In crystalline solids the particles repeat in a regular pattern; in amorphous solids (like glass) they do not. The smallest repeating box is the unit cell. Simple cubic holds 1 particle, body-centred cubic 2 and face-centred cubic 4. By the bonds holding them, crystals are ionic, covalent network, molecular or metallic.
• Surface Tension, Angle of Contact and Capillary Rise – Molecules at a liquid's surface are pulled inward by their neighbours, so the surface behaves like a stretched skin. The extra energy stored per unit area of surface is the surface energy, and it equals the surface tension S (force per unit length, N/m). Where a liquid meets a solid, the angle of contact θ tells whether it wets the solid (θ < 90°, like water on glass) or not (θ > 90°, like mercury). Curved surfaces have extra pressure inside: 2S/r for a drop or air bubble in liquid, 4S/r for a soap bubble. In a thin tube the liquid rises (or falls) by h = 2S cosθ / (rρg).

3. Selective 3 Ch.3 Laws of thermodynamics

First law; energy conservation · Second law

• First Law of Thermodynamics – Internal energy U is the total energy of the molecules inside a system. It changes in only two ways: by heat Q (energy that flows because of a temperature difference) and by work W (energy moved by a force, like a moving piston). First law: ΔQ = ΔU + ΔW. Heat given to a gas partly raises its internal energy and partly lets it do work. Work by a gas at constant pressure is PΔV. For an ideal gas Cp − Cv = R.
• Second Law of Thermodynamics, Heat Engines and Refrigerators – The first law says energy is conserved; the second law says which way heat and energy can go. Heat flows by itself only from hot to cold (Clausius). No engine can turn all the heat it takes into work; some must be thrown into a colder body (Kelvin–Planck). A heat engine takes Q₁ from a hot source, does work W and rejects Q₂: efficiency η = W/Q₁ = 1 − Q₂/Q₁. A refrigerator uses work W to move Q₂ from cold to hot: COP α = Q₂/W. The best possible engine, the Carnot engine, has η = 1 − T₂/T₁.

4. Selective 3 Ch.4 Atomic structure and wave–particle duality

Black-body radiation · Photoelectric effect · Nuclear atom; hydrogen spectrum; Bohr model · Matter waves; quantum mechanics

• The Quantum Idea: Energy Comes in Packets – A hot object glows, and the old physics could not explain its colours. In 1900 Max Planck guessed that energy is exchanged only in small packets. One packet of light of frequency f carries E = hf, where h = 6.63 × 10⁻³⁴ J s. Such a packet of light is a photon. This one guess fixed the puzzle and started quantum physics.
• Photoelectric Effect and Einstein's Equation – When light of high enough frequency falls on a metal, electrons jump out at once. Light comes in packets called photons, each with energy E = hν. One photon gives all its energy to one electron: hν = φ + KEmax, where φ is the work function. Below the threshold frequency ν₀ = φ/h no electron comes out, however bright the light.
• Atoms: From Alpha Scattering to the Bohr Model – Rutherford shot alpha particles at thin gold foil and found that an atom is mostly empty, with a tiny, heavy, positive nucleus in the middle. Bohr then said the electron in hydrogen can move only on fixed orbits where its angular momentum is nh/2π. In orbit n the radius is 0.529 n² Å, the speed is (2.19 × 10⁶)/n m/s and the energy is −13.6/n² eV. When the electron jumps down, the energy difference comes out as light of one exact colour, which gives the line spectrum of hydrogen.
• Matter Waves and the de Broglie Relation – Light behaves like a wave and a particle. In 1924 Louis de Broglie said matter does the same: every moving particle has a wave with wavelength λ = h/p = h/mv. For a body of kinetic energy K, λ = h/√(2mK); for an electron accelerated through V volts, λ = 1.227/√V nm. Everyday objects have far too tiny a λ to notice, but electrons have λ about the size of atoms.

5. Selective 3 Ch.5 The nucleus

Composition; decay; half-life · Nuclear force; binding energy · Fission and fusion · "Elementary" particles

• Radioactivity: Alpha, Beta, Gamma and Half-Life – Some atomic nuclei are unstable. They give out radiation at random to become more stable. This is radioactive decay. Alpha (2 protons + 2 neutrons), beta (a fast electron) and gamma (a wave of energy) are the three main kinds. Half-life is the time for half of the unstable nuclei to decay.
• Nuclei: Size, Nuclear Force, Binding Energy, Fission and Fusion – A nucleus is made of Z protons and N neutrons (A = Z + N nucleons). Its radius is R = R₀A^(1/3) with R₀ ≈ 1.2 fm, so every nucleus has almost the same huge density. A very strong, short-range nuclear force holds the nucleons together. The nucleus weighs a little less than its loose parts; this mass defect Δm is the binding energy, E = Δm c² (1 u = 931.5 MeV). Binding energy per nucleon is highest near iron (A ≈ 56), so heavy nuclei give energy when they split (fission) and light nuclei give energy when they join (fusion).
• Particle Physics: Quarks, Leptons and the Standard Model – Particle physics studies the smallest building blocks of matter. Protons and neutrons are made of quarks. Electrons belong to a family called leptons. Every particle has an antiparticle. Particles feel four forces, and three of them are carried by messenger particles called bosons. All of this together is called the Standard Model.

6. Elective 1: Physics and society

Physics and human understanding (cosmology, Galileo, relativity, quanta) · Physics and social change (steam, electromagnetism, microelectronics, IT, nuclear tech) · Physics in civic life (energy, lasers, spaceflight)

• Physics and Human Understanding: Cosmology, Galileo, Relativity and Quanta – For thousands of years people thought Earth sat still in the middle of the sky. Careful watching, the telescope and experiments changed that. Galileo showed that we should test ideas with measurement. Later, Einstein showed that time and space depend on speed, and Planck showed that energy comes in small packets called quanta. Scientists from many countries built this story together.
• Physics and Society: Steam, Electricity, Chips and Nuclear Power – New physics ideas changed how people live. The steam engine turned heat into movement. The generator turned movement into electricity. Microchips shrank switches so a phone can hold billions of them. Nuclear fission turns a little mass into a lot of heat.
• Physics in Civic Life: Energy, Lasers, Fibre and Spaceflight – Physics runs through public life. Energy used is power times time (1 kWh = 1 unit on the bill). Light bounces along glass fibre to carry internet and phone calls. A laser beam is thin, straight and one colour. A rocket pushes gas down and is pushed up; a satellite is a body always falling but moving sideways fast enough to miss Earth.

7. Elective 2: Physics and technology

Medical technology (ultrasound, X-ray, CT, radiation) · New energy · New materials (nano, superconductors) · Information technology (smartphones, satellite positioning)

• Medical Physics: Ultrasound, X-ray, CT and Radiation Safety – Ultrasound sends sound pulses into the body and times the echoes: depth = speed × time ÷ 2. X-rays pass through the body and bone stops more of them, making a shadow picture. CT joins many X-ray views from all angles into slices. X-rays are ionising, so we cut the dose with short time, long distance and a shield. Ultrasound uses sound and is not ionising.
• Renewable Energy Sources – Non-renewable sources (coal, oil, gas, uranium) are used faster than nature makes them, and fossil fuels release CO₂. Renewable sources are refilled by nature: solar (photovoltaic cells and solar heating), wind (P ∝ v³), hydroelectric (P = η ρ g h Q), tidal, geothermal and biomass. Hydrogen fuel cells turn hydrogen and oxygen into electricity and water. Because sun and wind change, we need storage (batteries, pumped hydro) and a mix of sources. Every source has costs: land, materials, cost and effect on nature.
• New Materials: Nanomaterials, Superconductors and Functional Materials – Nanomaterials have pieces about 1 to 100 nm across. Splitting a solid into tiny pieces keeps the volume but makes the surface much larger, so properties change. A superconductor loses all electrical resistance below a critical temperature and pushes magnetic field out, so a magnet floats above it. Functional materials change in a useful way when heat, light, pressure or electricity acts on them.

8. Elective 3: Frontiers

Microscopic world (de Broglie, uncertainty, particles) · High-speed world (special and general relativity) · Cosmos (Big Bang, black holes, dark matter) · Unity of the world (four interactions)

• Matter Waves and the de Broglie Relation – Light behaves like a wave and a particle. In 1924 Louis de Broglie said matter does the same: every moving particle has a wave with wavelength λ = h/p = h/mv. For a body of kinetic energy K, λ = h/√(2mK); for an electron accelerated through V volts, λ = 1.227/√V nm. Everyday objects have far too tiny a λ to notice, but electrons have λ about the size of atoms.
• Special Relativity – Special relativity (Einstein, 1905) rests on two postulates: the laws of physics are the same in all inertial frames, and the speed of light in a vacuum, c ≈ 3.00 × 10⁸ m/s, is the same for every observer. It follows that moving clocks run slow (t = γt₀), moving objects are shorter along their motion (L = L₀/γ), and mass is a form of energy (E = mc²), with γ = 1/√(1 − v²/c²). At everyday speeds γ ≈ 1, so Newton's mechanics works; near c it fails.
• Cosmology: The Expanding Universe and the Big Bang – Cosmology is the study of the whole universe: its structure, history and future. Galaxies gather in groups, clusters and filaments around huge voids. Distant galaxies are moving away from us, faster the farther they are (Hubble's law, v = H₀d), because space itself is expanding. Running the expansion backwards leads to a hot, dense beginning about 13.8 billion years ago, the Big Bang. The main evidence is redshift, the cosmic microwave background and the amounts of hydrogen and helium. Most of the universe is dark matter and dark energy.

9. 高考 review

Comprehensive review

Coming soon