准晶体为什么能“有秩序却没有周期”？
How can a quasicrystal be ordered yet non-periodic?
普通晶体平移会重复，准晶体用如五角对称这类不允许周期重复的图案铺满空间，却仍高度有序。2011 年谢赫特曼因发现它获诺贝尔化学奖。
Ordinary crystals repeat on translation; quasicrystals tile space with patterns like fivefold symmetry that forbid periodicity yet stay highly ordered. Shechtman won the 2011 chemistry Nobel for discovering them.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
费曼,《费曼物理学讲义》第一至三卷,Addison-Wesley,1963-1965
Richard P. Feynman et al., The Feynman Lectures on Physics, Addison-Wesley, 1963-1965
独立核验依据 · Independent verification: 核验依据 2 ISBN 978-0-7382-0298-3 (2006 Pearson 版，原始版为1963-65 Addis
#准晶体 #非周期 #对称
量子霍尔效应为何如此精确？
Why is the quantum Hall effect so precise?
在极低温强磁场下，二维电子气的霍尔电阻被量子化为 h/(ne²) 的整数或分数倍，只依赖基本常数。von Klitzing 于 1980 年发现这一平台，如今被用于精确定义电阻单位欧姆。
At very low temperature and strong field, the Hall resistance of a two-dimensional electron gas is quantized as h/(ne²), depending only on fundamental constants. von Klitzing discovered these plateaus in 1980, and they now define the ohm precisely.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
von Klitzing 1980 年论文（1985 诺奖）；Ashcroft 与 Mermin《固体物理》
von Klitzing (1980, Nobel 1985); Ashcroft & Mermin, Solid State Physics
独立核验依据 · Independent verification: 核验依据 1 ISBN 9780030839931 (2022)
#量子霍尔效应 #整数量子化 #电阻标准
超流现象为什么没有黏性？
Why does superfluidity have no viscosity?
在极低温下，部分玻色子凝聚到同一个宏观量子态，整体可用一个相干波函数描述，因而能无阻力地流动。卡皮查 1938 年发现液氦-4 的超流，Leggett 系统发展了量子液体理论。
At extremely low temperature a fraction of bosons condenses into one macroscopic quantum state described by a coherent wavefunction, letting the fluid flow without resistance. Kapitza discovered superfluid helium-4 in 1938, and Leggett developed the quantum-liquid theory.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
卡皮查 1938 年论文；Leggett《量子液体》
Kapitza (1938); Leggett, Quantum Liquids
独立核验依据 · Independent verification: 核验依据 1 ISBN 9780198526438 (2006)
#超流 #玻色凝聚 #液氦
超导体为什么能零电阻导电？这还算普通电阻吗？
How can a superconductor carry current with zero resistance — what's going on?
1911年昂内斯发现汞降到4.2K时电阻突然消失，这完全是量子效应。1957年BCS理论给出解释：低温下，电子借助晶格振动（声子）两两配对成库珀对，库珀对作为整体相干地流动，不再被原子散射，电阻就变为零。超导体还会把磁感线完全排出体外（迈斯纳效应），磁悬浮列车正是靠它悬浮的。
In 1911 Kamerlingh Onnes found mercury's resistance vanishes abruptly at 4.2 K — a purely quantum phenomenon. The 1957 BCS theory explains it: at low temperatures electrons pair up through lattice vibrations (phonons) into Cooper pairs, which flow as one coherent quantum state without scattering off atoms, so resistance drops to exactly zero. Superconductors also expel magnetic field lines (the Meissner effect), which levitates maglev trains.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-10-03 · 2 条独立证据
来源 · Source
《费曼物理学讲义》第三卷（超导）
The Feynman Lectures on Physics, Vol. 3 (superconductivity)
独立核验依据 · Independent verification: 核验依据 2 ISBN 978-0-7382-0298-3 (2006 Pearson 版，原始版为1963-65 Addis
#超导 #库珀对 #BCS理论
玻色-爱因斯坦凝聚态是什么，怎么造出来？
What is a Bose-Einstein condensate, and how is it made?
把一群玻色子冷却到极接近绝对零度，它们会“凝结”进同一个最低量子态，像一个大原子。1995 年用激光与蒸发冷却首次实现，是宏观可见的量子态。
Cool a cloud of bosons to near absolute zero and they condense into one lowest quantum state, behaving like a single giant atom. First made in 1995 with laser and evaporative cooling, it is a quantum state visible at macroscopic scale.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
程守洙 江之永,《普通物理学》第七版,高等教育出版社,2016
Cheng Shouzhu and Jiang Zhiyong, General Physics, 7th ed., Higher Education Press, 2016
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787040429190（豆瓣书目条目: 普通物理学．上册）
#玻色爱因斯坦凝聚 #超冷 #玻色子
安德森局域化说的是电子在杂质里「迷路」的现象吗？
Does Anderson localization describe electrons getting 'lost' among impurities?
大体如此：在足够强无序（如随机分布的杂质势）中，本来能自由运动的电子波会被反复散射、相互干涉，最终被「囚禁」在很小区域内而无法导电，金属从而表现得像绝缘体。安德森1958年用无序晶格模型预言此效应，揭示无序本身也能导致局域化，他因此获1977年诺贝尔奖。
Essentially yes: in sufficiently strong disorder (e.g., randomly placed impurity potentials), electron waves that could roam instead get repeatedly scattered and interfere, becoming trapped in a tiny region and unable to conduct—a metal behaving like an insulator. Anderson predicted this in 1958 with a disordered-lattice model, showing disorder alone can localize, earning the 1977 Nobel Prize.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
程守洙 江之永,《普通物理学》第七版,高等教育出版社,2016
Cheng Shouzhu and Jiang Zhiyong, General Physics, 7th ed., Higher Education Press, 2016
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787040429190（豆瓣书目条目: 普通物理学．上册）
#安德森局域化 #无序系统 #电子局域
拓扑绝缘体有什么特别之处？
What is special about a topological insulator?
拓扑绝缘体体内是绝缘体，但表面受拓扑保护而存在导电态，且电子自旋与运动方向锁定，对外来无序非常鲁棒。Kane 与 Mele 在 2005 年提出理论，Hasan 与 Kane 于 2010 年作了权威综述。
A topological insulator is insulating in the bulk but conducts on its surface through topologically protected states where electron spin is locked to direction of motion, robust against disorder. Kane and Mele proposed the theory in 2005; Hasan and Kane reviewed it in 2010.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：此条未指向带版次的可引用著作（通识性内容、机构文件或未展开的英文书名），本库不提供独立书目出处；如需精确引用，需由编辑补全具体篇目与版次。
Kane 与 Mele 2005 年论文；Hasan 与 Kane 2010 年综述
Kane & Mele (2005); Hasan & Kane, Review (2010)
#拓扑绝缘体 #表面态 #自旋-动量锁定
激光和普通灯光差在哪里？它为什么能那么亮、那么直？
What makes laser light different from ordinary light, and why is it so bright and straight?
普通灯发出的光频率混杂、方向各异，而激光基于受激辐射：一个光子经过处于激发态的原子时，会诱发原子放出完全一样的光子——频率、相位、方向都相同，光子随之不断倍增。激光器里的光学谐振腔让光在两面反射镜间来回反射、反复放大，最后输出高度相干、准直性极好的光束。这样的光束可以被透镜聚焦到极小的一点，能量高度集中，所以能切割金属、做手术，也用于光纤通信。
Ordinary light mixes many frequencies and directions, while a laser works by stimulated emission: a photon passing an excited atom triggers an identical photon — same frequency, phase, and direction — and the cascade multiplies. An optical cavity bounces the light back and forth between mirrors, amplifying it into a highly coherent, well-collimated beam. Such a beam can be focused to a tiny spot, concentrating energy so tightly that it cuts steel, performs surgery, and carries signals through optical fibers.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-10-03 · 2 条独立证据
来源 · Source
《费曼物理学讲义》第三卷（受激辐射）
The Feynman Lectures on Physics, Vol. 3 (stimulated emission)
独立核验依据 · Independent verification: 核验依据 2 ISBN 978-0-7382-0298-3 (2006 Pearson 版，原始版为1963-65 Addis
#激光 #受激辐射 #谐振腔
石墨烯为什么被称为「神奇材料」，它特殊在哪？
Why is graphene called a 'wonder material,' and what is special about it?
石墨烯是单层碳原子以蜂窝状排列的二维晶体，电子在其中像无质量粒子一样以极高速度运动（狄拉克锥），因此导电导热极好、又异常强韧。它几乎透明却比钢结实得多，载流子迁移率远超硅。海姆与诺沃肖洛夫2004年用胶带剥离法获得，获2010年诺贝尔奖，开启了二维材料研究热潮。
Graphene is a single atomic layer of carbon in a honeycomb lattice where electrons move like massless particles at very high speed (Dirac cones), giving superb conductivity, heat transport, and remarkable strength. Nearly transparent yet stronger than steel, with mobility far above silicon. Geim and Novoselov isolated it with sticky tape in 2004, winning the 2010 Nobel Prize and launching 2D-materials research.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：著录含书名，但缺版次 / 出版社 / 年份中的一部分，需编辑补全后才能做独立比对。
诺贝尔物理学奖 2010（海姆与诺沃肖洛夫，石墨烯）；Geim & Novoselov, 《科学》2004
Nobel Prize in Physics 2010 (Geim & Novoselov, graphene); Geim & Novoselov, Science (2004)
#石墨烯 #二维材料 #狄拉克锥
液晶显示器里的液晶是怎么"变出"图像来的？
How does the liquid crystal inside an LCD display produce images?
液晶分子是介于液体与晶体之间的长条形分子，会随外加电场改变排列方向。每个像素由夹在两层偏光片之间的液晶层构成：自然光先被第一片偏光片变成偏振光，再穿过液晶层。不加电场时，液晶层把偏振方向旋转90度，光得以通过第二片偏光片；加上电场后分子直立、不再旋转偏振方向，光就被挡住。逐个像素调节电压就能控制透过光的强弱，再配以红绿蓝滤色片便组成彩色图像。液晶本身不发光，所以屏幕背面还有一层背光源。
Liquid-crystal molecules are rod-shaped, partway between liquid and solid, and reorient under an electric field. Each pixel sandwiches a liquid-crystal layer between crossed polarizers: incoming light is first polarized, then travels through the crystal. Without a field the layer rotates the polarization by 90° and light passes the second polarizer; with a field the molecules stand up, stop rotating the polarization, and the light is blocked. Controlling the voltage pixel by pixel tunes the transmitted intensity, and red-green-blue filters render color. Since the crystal emits no light, a backlight sits behind the panel.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
程守洙 江之永,《普通物理学》第七版,高等教育出版社,2016
Cheng Shouzhu and Jiang Zhiyong, General Physics, 7th ed., Higher Education Press, 2016
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787040429190（豆瓣书目条目: 普通物理学．上册）
#液晶 #偏振 #像素
中子自旋回波技术如何绕开谱仪中能量分辨率与束流强度的传统矛盾？
How does the neutron spin echo technique evade the conventional trade-off between energy resolution and beam intensity in spectrometers?
常规谱仪要靠压窄入射能带来换取高分辨率，束流损失很大。自旋回波把中子自旋用作内嵌时钟：样品前后的强磁场使其发生拉莫尔进动，弹性散射时两段相位恰好抵消，非弹性散射则留下正比于能量转移的净进动角。速度分散不再损害分辨率，能量分辨可达微电子伏以下，因而能研究纳秒尺度的慢弛豫，如高分子熔体缠结动力学与蛋白质结构域运动。
Conventional spectrometers buy high resolution by narrowing the incident energy bandwidth at a heavy flux penalty. Spin echo instead uses the neutron spin as a built-in clock: strong precession fields before and after the sample produce Larmor phases that cancel exactly for elastic scattering, while inelastic events leave a net precession proportional to the energy transfer. Velocity spread then no longer spoils the resolution, which reaches sub-microelectronvolt levels, making nanosecond-scale slow relaxations, such as polymer-melt entanglement dynamics and protein domain motions, measurable.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-11-04
来源 · Source
Mezei,《Neutron spin echo: A new concept in polarized thermal neutron techniques》,Zeitschrift für Physik A Hadrons and nuclei,1972 (DOI: 10.1007/bf01394523)
F. Mezei, 'Neutron spin echo: A new concept in polarized thermal neutron techniques', Zeitschrift für Physik A Hadrons and nuclei, 1972, DOI: 10.1007/bf01394523
独立核验依据 · Independent verification: 核验依据 1 Crossref DOI 10.1007/bf01394523
#中子自旋回波 #拉莫尔进动 #慢动力学
为什么玻璃是透明的，金属却不透明？
Why is glass transparent while metal is opaque?
差别在电子能否吸收可见光。金属里有大量自由电子，它们会被光的电场推着振动，几乎瞬间把光反射回去，所以金属又亮又不透光。玻璃里的电子被束缚在原子上，能吸收光子的能量间隙远高于可见光，可见光光子能量不够，无法被吸收，就一路穿过去了，玻璃因而透明。
It comes down to whether electrons can absorb visible light. Metals swarm with nearly free electrons that respond to the light's electric field and instantly reflect it back, so metal is shiny and opaque. In glass the electrons are bound, and the energy gap where absorption happens lies in the ultraviolet; visible photons simply lack enough energy, pass straight through, and the glass looks transparent.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-10-03 · 2 条独立证据
来源 · Source
《费曼物理学讲义》第一卷（固体光学性质）
The Feynman Lectures on Physics, Vol. 1 (optical properties of solids)
独立核验依据 · Independent verification: 核验依据 2 ISBN 978-0-7382-0298-3 (2006 Pearson 版，原始版为1963-65 Addis
#能隙 #自由电子 #吸收
医院里的核磁共振（MRI）为什么需要超导磁体？
Why does a hospital MRI machine need a superconducting magnet?
MRI需要极强的磁场，通常为1.5到3特斯拉，约是地球磁场的数万倍，用来让体内的氢原子核整齐排列，再用射频脉冲激发并接收信号成像。磁场越强越稳定，图像越清晰。普通电磁铁要靠巨大的电流维持这样的场强，会大量发热；而超导线圈在低温下电阻为零，可以无损耗地长期维持强电流。所以医院的磁体要用液氦冷却到极低温度运行。
MRI needs an extremely strong field, typically 1.5 to 3 tesla — tens of thousands of times Earth's magnetic field — to align hydrogen nuclei in the body, then reads their signals after a radio-frequency pulse. Stronger, steadier fields give sharper images. An ordinary electromagnet running that much current would generate enormous heat; a superconducting coil has zero resistance at low temperature and can sustain the large current with no loss. That is why hospital magnets are chilled to cryogenic temperatures with liquid helium.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
程守洙 江之永,《普通物理学》第七版,高等教育出版社,2016
Cheng Shouzhu and Jiang Zhiyong, General Physics, 7th ed., Higher Education Press, 2016
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787040429190（豆瓣书目条目: 普通物理学．上册）
#核磁共振 #超导磁体 #磁场
橡胶为什么能当电线外皮，铜却不行？
Why can rubber coat wires while copper cannot?
铜的价电子松散、能自由流动，所以是良导体；橡胶的电子被牢牢绑在原子上，几乎不流动，是绝缘体。用橡胶包铜既导电又防触电。
Copper's outer electrons roam freely, so it conducts; rubber's electrons are tightly bound and barely move, so it insulates. Rubber around copper carries current yet keeps you safe from shock.
难度 进阶 · 适合 小学低段(6-8)
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
费曼,《费曼物理学讲义》第一至三卷,Addison-Wesley,1963-1965
Richard P. Feynman et al., The Feynman Lectures on Physics, Addison-Wesley, 1963-1965
独立核验依据 · Independent verification: 核验依据 2 ISBN 978-0-7382-0298-3 (2006 Pearson 版，原始版为1963-65 Addis
#导体 #绝缘体 #电子
盐和糖的“小颗粒”内部是怎么排列的？
How are the tiny grains of salt and sugar arranged inside?
它们是晶体，原子或离子按规则、重复的格子排布。食盐是钠离子与氯离子交替的立方晶格，所以易碎成小方块。
They are crystals, with atoms or ions in a regular, repeating lattice. Table salt is a cubic grid of alternating sodium and chloride ions, which is why it breaks into little cubes.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-10-04 · 2 条独立证据
来源 · Source
Charles Kittel 著《Introduction to Solid State Physics》（固体物理导论）
Charles Kittel, Introduction to Solid State Physics
独立核验依据 · Independent verification: 核验依据 1 ISBN 9780471490241 (2005) · 核验依据 2 ISBN 9780030839931 (2022)
#晶体 #晶格 #食盐
半导体为什么既不太导电也不太绝缘？
Why is a semiconductor neither a good conductor nor a good insulator?
固体里电子能级形成能带，半导体在满带与空带间只有很小的禁带。常温下少数电子能跳过去导电；升温或掺杂质后导电性大增，这正是芯片的基础。
In solids, electron levels form bands; a semiconductor has only a small gap between a filled band and an empty one. A few electrons cross at room temperature, and heat or doping boosts conductivity—the basis of chips.
难度 进阶 · 适合 小学高段(9-12)
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
费曼,《费曼物理学讲义》第一至三卷,Addison-Wesley,1963-1965
Richard P. Feynman et al., The Feynman Lectures on Physics, Addison-Wesley, 1963-1965
独立核验依据 · Independent verification: 核验依据 2 ISBN 978-0-7382-0298-3 (2006 Pearson 版，原始版为1963-65 Addis
#半导体 #能带 #禁带
液晶显示器（LCD）里的「液晶」到底是什么状态的物质？
What state of matter is the 'liquid crystal' inside an LCD?
液晶介于液体和晶体之间：分子能流动，却仍保持一定的取向有序，像被「排队」的液体。在电场作用下，液晶分子的排列会发生扭转或倾斜，从而改变对偏振光的透射，配合偏振片和彩色滤光片就能控制每个像素明暗与颜色。1960年代起 RCA 等机构发展出扭曲向列相显示，成为平板显示的主流。
Liquid crystals sit between liquid and crystal: the molecules flow yet keep orientational order, like a fluid that is 'lined up.' An electric field twists or tilts their arrangement, altering transmission of polarized light; with polarizers and color filters this controls each pixel's brightness and color. RCA and others developed twisted-nematic displays from the 1960s, making flat-panel displays mainstream.
难度 进阶 · 适合 小学高段(9-12)
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
程守洙 江之永,《普通物理学》第七版,高等教育出版社,2016
Cheng Shouzhu and Jiang Zhiyong, General Physics, 7th ed., Higher Education Press, 2016
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787040429190（豆瓣书目条目: 普通物理学．上册）
#液晶 #各向异性 #偏振光
为什么电脑芯片要用硅而不是导电更好的铜？
Why are computer chips made of silicon rather than a better conductor like copper?
因为硅是半导体：纯净的硅几乎不导电，但掺入极少量杂质（掺杂）后，导电能力能被精确控制。工程师利用这一点造出只让电流单向通过的二极管和可以开关、放大信号的晶体管，上亿个晶体管刻在一片硅晶圆上就是芯片。铜虽然导电好，却关不掉，只有导电性可精细调控的硅才能当开关用。
Because silicon is a semiconductor: pure silicon barely conducts, but doping it with a trace of impurities tunes its conductivity precisely. That enables diodes (one-way valves for current) and transistors (switches and amplifiers); etch billions onto a silicon wafer and you have a chip. Copper conducts better but can't be switched off — only silicon's controllable conductivity makes the on/off logic of computing possible.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
费曼,《费曼物理学讲义》第一至三卷,Addison-Wesley,1963-1965
Richard P. Feynman et al., The Feynman Lectures on Physics, Addison-Wesley, 1963-1965
独立核验依据 · Independent verification: 核验依据 2 ISBN 978-0-7382-0298-3 (2006 Pearson 版，原始版为1963-65 Addis
#半导体 #掺杂 #晶体管
为什么磁铁烧热到一定程度就失去磁性？
Why does a heated magnet lose its magnetism past a point?
铁磁体里小磁畴原本整齐排列，温度升到居里点（如铁约 770℃）时热运动打乱了秩序，整体磁性消失，只留下顺磁性。
In a ferromagnet the tiny domains are neatly aligned; once heated to its Curie point (about 770°C for iron), thermal motion scrambles the order and the net magnetism vanishes, leaving only paramagnetism.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-11-03
来源 · Source
P. Curie, 《Propriétés magnétiques des corps à diverses températures》, Annales de la faculté des sciences de Toulouse 7, 1 (1895)
P. Curie, 'Propriétés magnétiques des corps à diverses températures', Annales de la faculté des sciences de Toulouse 7, 1 (1895)
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL1096583W：Propriétés magnétiques
#铁磁性 #居里温度 #磁畴
磁悬浮列车是怎样悬浮在轨道上方的？
How does a maglev train levitate above its track?
上海磁悬浮列车采用电磁吸力悬浮：车底的电磁铁被轨道上的磁体吸引，控制系统实时调节电流，让列车稳定悬在约一厘米高处。而超导磁悬浮则利用超导体的完全抗磁性：超导线圈通入电流形成强磁场，轨道上感生的电流与之排斥，列车便被托起。由于超导线圈没有电阻，能长期维持强大电流而不发热，使悬浮既稳定又节能。
Shanghai's maglev train uses electromagnetic attraction: electromagnets under the car are pulled toward the track, and a control system continuously adjusts the current to hold the train about a centimeter above the rail. Superconducting maglev instead exploits the perfect diamagnetism of superconductors: superconducting coils carry a persistent current that creates a strong field, and currents induced in the track repel it, lifting the train. Because the coils have zero resistance, they hold huge currents without heating, keeping the levitation stable and efficient.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
程守洙 江之永,《普通物理学》第七版,高等教育出版社,2016
Cheng Shouzhu and Jiang Zhiyong, General Physics, 7th ed., Higher Education Press, 2016
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787040429190（豆瓣书目条目: 普通物理学．上册）
#磁悬浮 #超导 #抗磁性
发光二极管（LED）为什么能发光？
Why do light-emitting diodes (LEDs) emit light?
LED 由半导体 p-n 结构成，通电时电子与空穴在结区复合，释放的能量等于带隙，以光子形式射出。带隙越宽发出的光波长越短，因此改变材料就能调控颜色。
An LED is a semiconductor p-n junction; when biased, electrons and holes recombine in the depletion region and release energy equal to the band gap as a photon. A wider gap gives a shorter wavelength, so changing the material tunes the color.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-10-04 · 2 条独立证据
来源 · Source
Kittel《固体物理导论》；Shockley 1949 年论文
Kittel, Introduction to Solid State Physics; Shockley (1949)
独立核验依据 · Independent verification: 核验依据 1 ISBN 9780471490241 (2005) · 核验依据 2 ISBN 9780030839931 (2022)
#LED #带隙 #电子空穴复合
打火机的电子点火、石英表和麦克风，靠什么把机械能和电能互相转换？
What lets electronic lighters, quartz watches and microphones convert between mechanical and electrical energy?
靠的是压电效应：某些晶体（如石英）被挤压变形时，内部的电荷中心发生错位，晶体表面就会出现电压；反过来，给晶体加上电压又会让它产生形变。电子打火器用力按压晶体，瞬间产生上万伏的高压火花；石英表用交变电压驱动晶体稳定振动来计时；麦克风则让声波压迫晶体，把声音变成电信号。压电材料因此成为传感器和超声设备的核心。
The piezoelectric effect: in crystals like quartz, squeezing distorts the lattice so charge centers separate, producing a voltage across the faces — and applying a voltage makes the crystal deform instead. Electronic lighters strike a crystal to fire tens of thousands of volts; quartz watches drive the crystal with alternating voltage so its stable vibration keeps time; microphones let sound waves press a crystal into an electrical signal. Piezoelectrics are therefore the heart of sensors and ultrasonic devices.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
程守洙 江之永,《普通物理学》第七版,高等教育出版社,2016
Cheng Shouzhu and Jiang Zhiyong, General Physics, 7th ed., Higher Education Press, 2016
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787040429190（豆瓣书目条目: 普通物理学．上册）
#压电效应 #石英 #传感器
当二氧化碳的温度和压强被调到接近临界点时，原本透明的流体会突然变得像牛奶一样浑浊发白，这是什么原因造成的？
When carbon dioxide is taken close to its critical point in temperature and pressure, the transparent fluid suddenly turns as turbid and white as milk. What causes this?
这叫临界乳光。逼近临界点时气液差异消失，压缩率发散，密度涨落的关联长度增长到宏观尺度；那些尺寸与可见光波长相当且不断演化的涨落团把各方向的光强烈散射，流体便呈乳白。这类连续相变具有普适性：临界行为只取决于空间维数与序参量对称性，重整化群理论据此统一解释了各种体系的临界指数。
It is called critical opalescence. Near the critical point liquid and gas cease to differ, the compressibility diverges, and density fluctuations become correlated over macroscopic distances. Clusters of fluctuation comparable in size to visible wavelengths scatter light strongly in all directions, turning the fluid milky white. Such continuous transitions are universal: the critical behavior depends only on spatial dimension and order-parameter symmetry, which is how renormalization-group theory accounts for the shared critical exponents of very different systems.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
H. E. Stanley,Introduction to Phase Transitions and Critical Phenomena,Oxford University Press,1971
H. E. Stanley, Introduction to Phase Transitions and Critical Phenomena, Oxford University Press, 1971
独立核验依据 · Independent verification: 核验依据 1 DOI 10.1088/0031-9112/23/4/018
#相变 #临界乳光 #临界涨落