单透镜成像为什么会有色差？工程上怎么克服它？
Why do single lenses suffer chromatic aberration, and how do engineers correct it?
玻璃的折射率随波长变化，所以蓝光和红光经过同一透镜后会聚在不同位置，像的边缘出现彩色，这就是色差。经典解决方案是消色差双合透镜：把折射率与色散能力不同的两种玻璃胶合在一起，让两者的色散相互抵消，使两种波长的光会聚到同一点。此外还有球差、彗差、像散等几何像差，需要用多片透镜组合和特殊面型来校正。
Because a lens's refractive index depends on wavelength, blue and red light focus at different points, smearing the image edges with color — chromatic aberration. The classic fix is an achromatic doublet, two lenses of different dispersion glued together so their color shifts cancel and two wavelengths focus together. Other geometric aberrations, such as spherical aberration, coma and astigmatism, call for multi-element designs and aspheric surfaces.
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》第一卷（色差）
The Feynman Lectures on Physics, Vol. 1 (chromatic aberration)
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
#色差 #消色差 #像差
激光为什么能保持一条极细的光束传很远，而普通灯光很快发散开？
Why can a laser stay a narrow beam over long distances while ordinary light spreads out quickly?
激光的光子几乎同频率、同相位、同方向，这种高度的空间与时间相干性让它以稳定的高斯光束传播、几乎不发散。普通光源发出的光相位杂乱、方向各异，所以迅速散开。相干性也正是激光能用于精密测距和全息的原因。
Laser light consists of photons with nearly the same frequency, phase, and direction; this strong spatial and temporal coherence lets it propagate as a stable Gaussian beam that hardly diverges. Ordinary sources emit light with random phases and directions, so they spread quickly. Coherence is also why lasers enable precise ranging and holography.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
O. Svelto,《Principles of Lasers》(第5版),第1章(相干性)
O. Svelto, 'Principles of Lasers' (5th ed.), Ch.1 (Coherence)
独立核验依据 · Independent verification: 核验依据 1 ISBN 9781461576716 (2016)
#相干性 #高斯光束 #激光
为什么光盘表面在光下会显现出彩虹般的条纹？
Why does a CD surface show rainbow-like stripes under light?
光盘表面有极密的同心纹轨，相当于反射光栅。白光被这些细微结构衍射并分光，不同方向看到不同波长的加强，于是呈现彩虹色。
A CD has extremely fine concentric tracks that act as a reflection grating. White light is diffracted and separated by these tiny structures, and different viewing angles show reinforced different wavelengths, producing rainbow colors.
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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#衍射 #光栅 #光学
全内反射的临界角由什么决定，光纤如何利用它？
What sets the critical angle for total internal reflection and how do fibers use it?
当光从折射率 n1 介质射向 n2<n1 介质且入射角超过 θc=arcsin(n2/n1) 时发生全内反射，无透射损耗。光纤用高-低折射率包层把光约束在纤芯里反复全反射传输。
Beyond θc=arcsin(n2/n1) light is totally reflected with no transmission loss. Fiber optics use a lower-index cladding to trap light in the core by repeated total internal reflection.
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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#光学 #全内反射 #光纤
激光和普通灯光最根本的区别是什么？
What is the fundamental difference between a laser and ordinary light?
激光来自受激辐射，所有光子频率、相位、方向一致，是高度相干的单色窄束；普通灯是大量原子随机发光，杂乱不相干。这束“一致的光”才能精确切割与测距。
Laser light comes from stimulated emission, so all photons share frequency, phase, and direction—a coherent, monochromatic, narrow beam. Ordinary lamps emit random, incoherent light from countless atoms. That ordered beam is what allows precise cutting and ranging.
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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#激光 #受激辐射 #相干
为什么沙漠或炎热路面上有时会看到远处的池水或晃动景象？
Why do deserts or hot roads sometimes show a fake pool of water or shimmering scene in the distance?
靠近炙热地面的空气密度小、折射率低，上层空气密度大。光线穿过密度梯度时发生弯曲，把天空或远处景物弯到地面附近，形成下现蜃景，看起来像水面反光。
Air just above a hot surface is less dense with a lower refractive index than the cooler layer above. Light bends through this gradient, curving the sky or distant objects down near the ground, creating a lower mirage that looks like a reflective pool.
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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#折射 #密度梯度 #光学
全息照片为什么有立体感？它和普通照片的记录方式有什么不同？
Why do holograms look three-dimensional, and how does their recording differ from ordinary photography?
普通照片只记录光的强度，丢失了相位信息。全息拍摄让物体反射的光与一束参考光在感光材料上发生干涉，把光场的振幅和相位一并编码成干涉条纹。用参考光照射这张图样时，干涉条纹会重新放出物体原来的光波，观察者移动视角时能看到视差，获得真实的立体感。钞票防伪全息图也是同样的干涉原理。
An ordinary photograph records only intensity and throws away phase. In holography, light scattered by the object interferes with a reference beam on the recording material, encoding both amplitude and phase as interference fringes. Illuminating that pattern with the reference beam reconstructs the object's original wavefront, and moving your viewpoint reveals real parallax, so the image looks solid. The holograms on banknotes use the same interference principle.
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》第一卷（全息）
The Feynman Lectures on Physics, Vol. 1 (holography)
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
#全息 #干涉 #相位
为什么偏振太阳镜能减弱水面或路面的刺眼反光？
Why do polarized sunglasses reduce the glare from water or roads?
反光多为特定方向的偏振光，偏振镜片只允许与其透光轴一致方向的光通过，挡住大部分水平偏振的反射光。于是刺眼反光被削弱，景物更清晰。
Reflected glare is largely polarized in one direction, and a polarizing lens only passes light aligned with its transmission axis, blocking most of that horizontally polarized reflection. The glare is cut and the view becomes clearer.
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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#偏振 #反射 #光学
衍射光栅为什么能把白光精确地分解成光谱？
Why does a diffraction grating split white light into precise spectra?
光栅表面刻有数千条间距均匀的细槽，每条槽的衍射光之间发生干涉，只有在相邻光程差恰好等于整数倍波长的方向才会出现明亮的谱线。由于这个条件依赖波长，不同颜色的光被送到不同角度，白光因此被展开成光谱。光栅的角分辨率远高于棱镜，还能同时看到多级光谱，所以光谱仪普遍用它来分析星光和物质的成分。
A grating carries thousands of evenly spaced grooves, and the light diffracted from them interferes: bright lines appear only in directions where the path difference between neighboring grooves is an integer number of wavelengths. Because that condition depends on wavelength, each color emerges at its own angle and white light fans into a spectrum. Gratings resolve angles far better than prisms and show multiple orders, which is why spectrometers use them to analyze starlight and material composition.
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》第一卷（衍射光栅）
The Feynman Lectures on Physics, Vol. 1 (diffraction gratings)
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
#衍射光栅 #光谱仪 #干涉
激光是什么，为什么它又细又亮？
What is a laser and why is its beam so narrow and bright?
激光是受激辐射产生的光，所有光子频率、方向、相位一致（相干），所以能汇聚成极细、极亮、几乎不发散的光束。
A laser uses stimulated emission to make photons with identical frequency, direction, and phase (coherent), yielding an intense, narrow, non-spreading beam.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Svelto，《激光原理》（第5版）
Svelto, 'Principles of Lasers' (5th ed.)
独立核验依据 · Independent verification: 核验依据 1 ISBN 9781461576716 (2016)
#激光 #相干 #受激辐射
为什么同样功率的绿色激光笔看起来比红色激光笔更亮？
Why does a green laser pointer look brighter than a red one of the same power?
人眼在555纳米附近的黄绿光最敏感，对绿光（约532纳米）的感知效率远高于红光（约650纳米）。相同光功率下进入眼睛被感受的亮度就更强。
The human eye is most sensitive near 555 nm, and it perceives green light around 532 nm far more efficiently than red around 650 nm. At the same optical power, the green appears much brighter to us.
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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#视敏度 #波长 #光学
迈克尔逊干涉仪是怎么测出比波长还小的长度变化的？
How does a Michelson interferometer measure length changes far smaller than the wavelength?
一束光经分光镜分成两路，分别射向两面镜子后返回并重新会合，两臂的光程差决定干涉条纹的明暗。只要一面镜子移动半个波长，光的往返光程就变化一个波长，条纹恰好移动一个完整周期，因此亚微米乃至更小的位移都能被精确读出。引力波探测器LIGO正是把这一原理放大到数公里长的双臂，测出了比原子核直径还小的时空伸缩。
A beam splitter divides light into two arms that reflect off mirrors and recombine, and the arm-length difference sets the interference pattern. Moving one mirror by half a wavelength changes the round-trip path by a full wavelength, shifting the fringes by exactly one period, so displacements far below a micron are readable. The gravitational-wave detector LIGO scales the same idea to multi-kilometer arms and senses stretches smaller than an atomic nucleus.
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》第一卷（迈克尔逊干涉仪）
The Feynman Lectures on Physics, Vol. 1 (the Michelson interferometer)
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
#干涉仪 #光程差 #LIGO
双缝实验里，一个光子到底通过了哪条缝？
In the double-slit experiment, which slit does a single photon go through?
若不观测，单个光子表现出通过两缝的叠加，在屏上积累出干涉条纹；一旦在缝处测量它走哪条，干涉图样就消失。这说明“路径”并非事先确定的经典属性。
Left unobserved, a single photon behaves as going through both slits at once, building an interference pattern; measure which slit it takes and the pattern vanishes. The path is not a pre-set classical property.
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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#双缝 #干涉 #波粒二象性
为什么白天的天空看起来是蓝色的，而日落时又偏红？
Why does the daytime sky look blue, yet turn reddish at sunset?
阳光中的短波蓝光比长波红光更容易被空气分子散射（瑞利散射），所以天空弥漫蓝光。日落时阳光斜穿更厚的大气，蓝光被散射殆尽，剩下红橙光直达眼睛。
Air molecules scatter short-wavelength blue light far more than long-wavelength red (Rayleigh scattering), filling the sky with blue. At sunset the light passes through more atmosphere, scattering away the blue and leaving red-orange to reach your eyes.
难度 专业 · 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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#瑞利散射 #光学 #大气
为什么游泳池看起来比实际深度要浅？
Why does a swimming pool look shallower than it really is?
从水底发出的光在界面折射后偏离法线，人眼沿直线反推会把它估计到更浅的位置，形成视深小于实深。视深约为实深的四分之三左右（取决于折射率）。
Light from the bottom refracts away from the normal at the surface, and the eye traces it straight back to a shallower apparent position, so apparent depth is less than real depth, roughly three quarters of it depending on the refractive index.
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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#折射 #视深 #光学
同轴全息再现实像时总会伴生一个无法去除的共轭像，离轴参考光是如何把它们分开的？
Inline holography always reconstructs the wanted image together with an inseparable conjugate twin; how does an off-axis reference beam separate them?
同轴记录时物波与参考波共线，再现后正负一级衍射沿同一光轴传播，原始像与共轭像完全重叠。利斯与厄帕尼克斯让参考平面波以倾角入射，全息条纹相当于给物波信息叠加了空间载频；再现时零级与正负一级沿不同方向分离。只要载频超过物光空间带宽约三倍，用光阑单独滤出一级衍射，就能得到不受共轭像污染的重构。
In inline recording the object and reference waves share one axis, so after reconstruction the plus and minus first diffraction orders propagate along that axis and the true image sits exactly atop its conjugate. Leith and Upatnieks tilted the reference plane wave; the recorded fringes impose a spatial carrier on the object information, and at reconstruction the zero and both first orders travel in separated directions. Once the carrier exceeds about three times the object's spatial bandwidth, an aperture isolating one order yields a reconstruction free of conjugate contamination.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-11-02
来源 · Source
E. N. Leith与J. Upatnieks：重建波前与通信理论，Journal of the Optical Society of America第52卷1123页（1962年），DOI 10.1364/JOSA.52.001123
E. N. Leith & J. Upatnieks, reconstructed wavefronts and communication theory, Journal of the Optical Society of America 52, 1123 (1962), DOI 10.1364/JOSA.52.001123
独立核验依据 · Independent verification: 核验依据 1 CROSSREF 标识 10.1364/josa.52.001123：Reconstructed Wavefro
#全息术 #离轴参考光 #空间载频
超短光脉冲在光纤里传播数千公里仍然不弥散开，光孤子究竟是靠什么机制维持住自己的形状的？
An ultrashort light pulse can travel thousands of kilometers in optical fiber without smearing out. What mechanism lets an optical soliton hold its shape?
靠色散与自相位调制的精确抵消。克尔效应使光纤折射率随光强变化，强脉冲因此给自己附加随时间变化的相位调制，前沿偏红、后沿偏蓝；在反常色散区蓝移成分跑得更快，这一啁啾引起的压缩恰好抵消色散带来的展宽。两者平衡时脉冲成为孤子，可长距离稳定传输。1980年贝尔实验室首次在光纤中观测到光孤子，奠定了孤子通信的基础。
An exact cancellation of dispersion by self-phase modulation. Through the Kerr effect the fiber's refractive index depends on intensity, so the pulse imposes a transient phase modulation on itself, red-shifting its leading edge and blue-shifting its trailing edge. In the anomalously dispersive regime bluer components travel faster, and the resulting chirp compresses the pulse exactly where dispersion would broaden it. When the two balance, the pulse becomes a soliton that propagates stably over vast distances. Bell Laboratories first observed optical solitons in fiber in 1980, laying the groundwork for soliton communication.
难度 专业 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-11-04
来源 · Source
A. Hasegawa,F. Tappert,Applied Physics Letters,1973；L. F. Mollenauer et al.,Physical Review Letters,1980
A. Hasegawa & F. Tappert, Applied Physics Letters, 1973; L. F. Mollenauer, R. H. Stolen & J. P. Gordon, Physical Review Letters, 1980
独立核验依据 · Independent verification: 核验依据 1 Crossref DOI 10.1103/physrevlett.45.1095（复合著录按段核验：本标识只担保
#光孤子 #光纤通信 #克尔效应
光为什么既有波动性又有粒子性？
Why does light behave both like a wave and like a particle?
光在传播、干涉和衍射中表现出波动性，在与物质相互作用如光电效应中表现出粒子性，这种现象称为波粒二象性。这是量子物理的核心观念之一。
Light shows wave behavior in propagation, interference, and diffraction, yet particle behavior in interactions like the photoelectric effect; this is wave-particle duality, a core idea of quantum physics.
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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#波粒二象性 #量子 #光
光在光纤里为什么能沿着弯曲的玻璃丝“拐弯”前进，却几乎不从侧壁漏出去？
Why can light travel around bends inside a glass fiber without leaking out the sides?
当光在纤芯与包层的界面上以大于临界角的角度入射时，会发生全内反射，光被完全反射回纤芯。只要弯曲不太剧烈，光就在一连串全反射中向前传，损耗极低。这正是光纤通信能远距离传信号的基础。
When light hits the core–cladding boundary at an angle greater than the critical angle, it undergoes total internal reflection and is completely reflected back into the core. As long as bends are not too sharp, light advances through a cascade of such reflections with very low loss. This is the basis of long-distance fiber communication.
难度 进阶 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
G. Keiser,《Optical Fiber Communications》(第5版),第2章(光纤波导)
G. Keiser, 'Optical Fiber Communications' (5th ed.), Ch.2 (Optical fiber waveguides)
独立核验依据 · Independent verification: 核验依据 1 ISBN 9780071007856 (2000)
#全内反射 #光纤 #临界角
最小作用量原理在光学中如何体现为费马原理？
How does the principle of least action appear in optics as Fermat's principle?
费马原理说，光线在两点间走的路径使传播时间取极值（通常最小）。由此可推导出反射定律和折射定律。它是最小作用量思想在光学中的早期体现，比力学形式早了很久。
Fermat's principle states that light takes the path between two points that makes travel time extremal (usually minimal). From it one derives the laws of reflection and refraction. It is an early embodiment of the least action idea in optics, long before its mechanical form.
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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#费马原理 #光程 #最小作用量
干涉和衍射有什么联系与区别？
What is the relation and difference between interference and diffraction?
干涉是多束相干波叠加产生强弱分布，衍射是波遇到障碍或缝隙时偏离直线传播。本质上衍射可视为无数子波的干涉。两者都源于波的叠加原理。
Interference is the strong-and-weak pattern from superposing several coherent waves, while diffraction is a wave bending around obstacles or through apertures. In essence diffraction can be seen as interference of countless sub-waves. Both arise from the superposition principle.
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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#干涉 #衍射 #叠加原理
牛顿用三棱镜把白光分成七色，这是为什么？
Why did Newton split white light into a rainbow of colors with a prism?
白光本身是多种波长光的混合。玻璃对不同波长光的折射程度不同：紫光波长最短、被折射得最厉害，红光波长最长、偏折最轻。于是白光通过棱镜后，各种颜色沿不同方向散开，展开成红橙黄绿蓝靛紫的光谱。雨后的彩虹也是阳光在雨滴中发生同样色散的结果。
White light is a mixture of many wavelengths, and glass bends each one a little differently: violet, the shortest wavelength, is refracted most, while red, the longest, is bent least. So after passing through a prism the colors fan out at different angles into a red-to-violet spectrum. Rainbows are sunlight undergoing the same dispersion inside raindrops.
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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#色散 #折射率 #光谱
夏天在滚烫的沙漠公路上，为什么远处会出现一滩"水"？
Why does a hot desert road appear to have a pool of water in the distance on summer days?
接近地面的空气被晒得膨胀、密度变小，而上层空气相对更冷更密。光从较密的空气斜射入较疏的空气时发生弯折，甚至可以发生全反射，来自天空的光线被一路弯向上、进入观察者的眼睛，看起来就像地面有一滩水在反射天空。这种幻影是温度梯度引起的折射现象。
Air near the scorching ground expands and becomes less dense than the cooler air above. Light moving from dense to rare air bends, and can even undergo total internal reflection, so rays from the sky curve upward into the observer's eye and look like a pool reflecting the sky. This mirage is refraction caused by the temperature gradient.
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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#海市蜃楼 #折射 #全反射
光的偏振是什么意思？
What does polarization of light mean?
自然光的电场振动方向杂乱，偏振光则只沿某一个固定方向振动。马吕斯 1808 年发现偏振光通过检偏器后强度随夹角平方变化，偏振现象证明光是横波。
In ordinary light the electric field vibrates in all directions, while polarized light vibrates only along one fixed direction. Malus showed in 1808 that polarized light through an analyzer dims as the cosine squared of the angle—evidence that light is a transverse wave.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：著录仅给书名，无版次与年份；同一书名常对应多个版次，不臆测具体版本。
马吕斯 1808 年论文；Hecht《光学》
Malus (1808); Hecht, Optics
#偏振 #横波 #马吕斯定律
什么是全内反射？
What is total internal reflection?
当光从光密介质射向光疏介质，且入射角大于临界角时，光全部反射回原介质，不折射出去，这就是全内反射。光纤正是利用此原理传输信号。
When light goes from a denser to a rarer medium at an angle above the critical angle, it is entirely reflected back with no refraction; this is total internal reflection. Optical fibers rely on it to carry signals.
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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#全内反射 #光纤 #临界角
透镜是怎样成像的？
How do lenses form images?
凸透镜能使平行光线会聚到焦点，可成放大或缩小的实像，常用于照相机和眼镜；凹透镜使光线发散，常用于矫正近视。
A convex lens focuses parallel light to a point and can form enlarged or reduced real images, used in cameras and eyeglasses; a concave lens diverges light and corrects near-sightedness.
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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#透镜 #成像 #焦距
两块偏振方向互相垂直的偏振片叠在一起光就全黑，可中间再夹一块斜放的偏振片，为什么光又能透过去了？
Two crossed polarizers block all light, so why does inserting a third polarizer at an angle let light through again?
第一片让光变成沿其透光轴的线偏振光，第二片与之垂直时按马吕斯定律 cos²90°=0，光被完全挡住。插入的中间片与第一片成 θ 角，会把光重新变成沿自身轴的线偏振光（强度按 cos²θ 减小），这个新方向与第三片不再垂直，于是还有 cos²(90°−θ) 的分量能透过。偏振片不是开关，而是把偏振态投影到自己的轴上，方向被逐级“扭转”。
The first polarizer makes the light linearly polarized along its transmission axis, and a second axis at 90° blocks it completely because Malus's law gives cos²90° = 0. A middle sheet at angle θ re-polarizes the light along its own axis with intensity cut by cos²θ, and that new direction is no longer perpendicular to the third sheet, so a cos²(90°−θ) fraction still gets through. A polarizer is not an on/off gate: it projects the polarization onto its own axis, rotating the direction step by step.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：著录仅给书名，无版次与年份；同一书名常对应多个版次，不臆测具体版本。
E. Hecht,《Optics》(第5版),第8章(偏振)
E. Hecht, 'Optics' (5th ed.), Ch.8 (Polarization)
#偏振 #线偏振 #马吕斯定律
为什么凸透镜能把远处景物的像清清楚楚地投在光屏上？
Why can a convex lens project a sharp image of a distant scene onto a screen?
凸透镜对光有会聚作用：平行于主光轴的光线经折射后都汇聚到焦点，物体上同一点发出的光经过透镜后会重新会聚到同一个像点，于是物体的像被完整重建。物体位于二倍焦距以外时，另一侧形成倒立、缩小的实像；位于焦点与二倍焦距之间时则形成倒立、放大的实像。物体越远，像越靠近焦点。
A convex lens converges light: rays parallel to the axis bend toward the focal point, and light from each point of the object is refocused to a matching image point, so the whole image is rebuilt. An object beyond twice the focal length forms an inverted, reduced real image on the far side; between the focus and twice the focal length it forms an inverted, magnified real image. The farther the object, the closer the image sits to the focal point.
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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#凸透镜 #成像 #焦点
为什么天空是蓝的而夕阳是红的？
Why is the sky blue but sunsets red?
瑞利散射强度∝1/λ⁴，短波蓝光比红光更易被空气分子散射到各方向，所以白天天穹泛蓝；日落时阳光穿过更厚大气，蓝绿被散射掉，剩下红橙直达眼睛。
Rayleigh scattering ∝1/λ⁴ favors blue, so the daytime sky looks blue; at sunset the long path scatters away blue, leaving red-orange.
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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#光学 #散射 #天空颜色
光通过很窄的狭缝后，为什么光斑比缝本身宽得多，还会出现条纹？
Why does light passing through a very narrow slit spread far wider than the slit and show fringes?
这是衍射：波遇到障碍物边缘会绕过它继续传播。当缝宽小到与波长可比时，狭缝上各点发出的子波在远处互相叠加，某些方向加强、某些方向抵消，于是形成中央亮斑和两侧明暗相间的条纹。缝越窄衍射越明显，这也是观察衍射通常要求狭缝很窄的原因。
This is diffraction: waves bend around the edges of obstacles. When the slit is comparable in width to the wavelength, secondary waves from different parts of the slit interfere in the far field, reinforcing in some directions and cancelling in others, producing a bright central band with fringes on both sides. The narrower the slit, the stronger the diffraction.
难度 进阶 · 适合 初中(12-15)
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（衍射）
The Feynman Lectures on Physics, Vol. 1 (diffraction)
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
#单缝衍射 #惠更斯原理 #条纹
非线性光学中的倍频（SHG）为什么需要非中心对称晶体？
Why does second-harmonic generation need a non-centrosymmetric crystal?
二阶非线性极化 P(2ω)=χ⁽²⁾E² 要求 χ⁽²⁾ 非零，而具有中心对称的晶体在反演下 E² 不变、P 变号，迫使 χ⁽²⁾=0；只有非中心对称晶体（如BBO、KDP）能产生倍频。
Second-order polarization P(2ω)=χ⁽²⁾E² needs nonzero χ⁽²⁾; centrosymmetric crystals force χ⁽²⁾=0 under inversion, so only non-centrosymmetric crystals (BBO, KDP) yield SHG.
难度 进阶 · 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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#光学 #非线性光学 #倍频
什么是相干长度，为什么干涉实验需要它？
What is coherence length and why do interference experiments need it?
相干长度是光波能维持固定相位关系的距离（≈λ²/Δλ）；若光程差超过它，两束光相位随机，干涉条纹消失，所以迈克耳孙等干涉仪要求程差在相干长度内。
Coherence length is the distance over which phase stays correlated (≈λ²/Δλ); if path difference exceeds it, fringes vanish, so interferometers must keep path differences within it.
难度 进阶 · 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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#光学 #相干 #干涉
全息照片和普通照片有什么本质不同，为什么换个角度看还能看到立体？
How does a hologram fundamentally differ from a normal photo, and why does it look 3D from different angles?
普通照片只记录光的强度，全息则同时用一束参考光与物光干涉，把物体反射光的「振幅和相位」都刻在底片上。相位信息保存了光从哪里来、走了多远，因此用同样波长的光照射时，能重建出具有视差和景深的立体波前。伽博1948年提出原理，并因此获1971年诺贝尔物理学奖。
A normal photo records only light intensity; a hologram uses a reference beam interfering with the object beam to etch both the amplitude and the phase of the reflected light onto the plate. Phase encodes where the light came from and how far, so illuminating it with the same wavelength reconstructs a 3D wavefront with parallax and depth. Gabor proposed it in 1948 and won the 1971 Nobel Prize in Physics.
难度 进阶 · 适合 小学高段(9-12)
CC BY 4.0 · 已核验 · Verified 2026-11-02
来源 · Source
诺贝尔物理学奖 1971（丹尼斯·伽博，全息术原理）；伽博 1948 年《自然》论文
Nobel Prize in Physics 1971 (Dennis Gabor, holography); Gabor (1948), Nature paper
独立核验依据 · Independent verification: 核验依据 1 CROSSREF 标识 10.1109/proc.1972.8723：Dennis Gabor [1971 No
#全息术 #干涉 #相位记录
杨氏双缝实验中，为什么屏幕上会出现明暗相间的条纹？
In Young's double-slit experiment, why do bright and dark fringes appear on the screen?
从两条狭缝透出的光在屏幕上相遇时会相互叠加：当两列波的波峰与波峰重合时振幅相加，形成亮纹；当波峰与波谷重合时相互抵消，形成暗纹。条纹的出现是光具有波动性的直接证据，而相邻亮纹的间距还反映了光的波长，波长越长条纹越宽。
Light from the two slits overlaps on the screen: when crests meet crests the amplitudes add to make a bright fringe, and when a crest meets a trough they cancel to make a dark one. The fringes are direct evidence that light is a wave, and their spacing encodes the wavelength — longer wavelengths give wider spacing.
难度 进阶 · 适合 初中(12-15)
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（干涉）
The Feynman Lectures on Physics, Vol. 1 (interference)
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
#干涉 #波动性 #波长
为什么把筷子斜插进水杯里，看起来像在水面处折断了？
Why does a chopstick look broken at the water surface when tilted in a glass?
光从水进入空气时速度改变，传播方向发生偏折，这就是折射。人眼沿直线回溯光线，就把水下那段筷子的虚像画到了实际位置上方，看起来折了。
Light changes speed going from water to air and bends, which is refraction. The eye traces the rays straight back, placing the underwater part's virtual image above its true position, so the chopstick looks bent.
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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#折射 #虚像 #光学
什么是反射和折射？
What are reflection and refraction?
反射是光遇到界面后按一定角度弹回的现象，如照镜子；折射是光从一种介质进入另一种介质时传播方向改变的现象，如筷子在水中看起来弯折。
Reflection is light bouncing off a surface at a definite angle, as in a mirror; refraction is the bending of light as it passes from one medium to another, making a submerged stick look bent.
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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#反射 #折射 #界面
什么是光的干涉和衍射？
What are interference and diffraction of light?
干涉是两束相干光叠加后形成明暗条纹的现象，衍射是光绕过障碍物边缘后发生展宽的现象。二者都证明光具有波动性。
Interference is the bright and dark pattern formed when two coherent light beams overlap, and diffraction is light spreading as it bends around obstacles. Both prove light's wave nature.
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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#干涉 #衍射 #波动性
3D 电影是怎么让我们看出立体感的？
How do 3D movies create a sense of depth?
左右眼看到略有差别的两幅画面，眼镜（偏振或快门）让每只眼只接收对应画面，大脑把差异合成出立体感。
Each eye sees a slightly different image; glasses (polarized or shutter) route the correct one to each eye, and the brain merges them into 3D depth.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-10-03 · 3 条独立证据
来源 · Source
Halliday、Resnick 与 Walker，《物理学基础》（第10版）
Halliday, Resnick & Walker, 'Fundamentals of Physics' (10th ed.)
独立核验依据 · Independent verification: 核验依据 2 angusrobertson.com.au
#3D #立体视觉 #偏振
为什么近视眼戴凹透镜能看清远处？
Why does a concave lens let a nearsighted person see far away?
近视眼眼球过长，远物成像落在视网膜前。凹透镜先让平行光发散一点，使焦点后移到视网膜上，于是远处变清晰。
A nearsighted eye is too long, so distant images focus in front of the retina. A concave lens spreads the parallel rays first, shifting the focus back onto the retina so distant things sharpen.
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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#透镜 #近视 #成像
为什么透过CD表面能看到彩虹色条纹？
Why do rainbow stripes appear on a CD surface?
CD表面的同心沟槽间距与光波长相近，构成反射衍射光栅；不同波长的光在不同角度加强，于是白光被分解成彩色条纹。
A CD's closely spaced tracks act as a reflection diffraction grating; different wavelengths reinforce at different angles, splitting white light into colored bands.
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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#光学 #衍射 #光栅
偏光太阳镜为什么能减少水面或玻璃的刺眼反光？
Why do polarized sunglasses cut the harsh glare reflected from water or glass?
自然光的振动方向是杂乱无章的，但被水面、玻璃等表面反射后，光会主要沿某一个方向振动，成为偏振光。偏光镜片只让特定振动方向的光通过，相当于一个会过滤方向的栅栏，把反射来的偏振光挡在外面，反光因此被削弱。钓鱼者和司机常靠它看清水面与路面。
Ordinary light vibrates in every direction, but after reflecting off water or glass it becomes polarized, vibrating mainly in one plane. A polarizing lens passes only light vibrating in one direction, acting like a grid that filters by orientation, so it blocks the reflected polarized light and kills the glare. Anglers and drivers use them to see into water and along roads.
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（偏振）
The Feynman Lectures on Physics, Vol. 1 (polarization)
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
#偏振 #眩光 #反射
相机和眼镜镜片上镀一层极薄的膜，为什么反而能减少反光、让更多光进入？
Why does a very thin coating on camera and eyeglass lenses reduce glare and let more light in?
这是薄膜干涉：薄膜上下两个界面反射的光路程差恰好为半个波长，两者相消，反射就被削弱。反射少了，进入镜片的光就更多、成像更清晰。膜厚通常取四分之一波长，正是为制造这种相消。
This is thin-film interference: light reflected from the top and bottom surfaces of the coating travels half a wavelength out of step and cancels, weakening reflection. With less reflected light, more enters the lens and the image is clearer. The film is typically a quarter-wavelength thick to produce exactly this cancellation.
难度 进阶 · 适合 小学高段(9-12)
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：著录仅给书名，无版次与年份；同一书名常对应多个版次，不臆测具体版本。
E. Hecht,《Optics》(第5版),第9章(薄膜干涉)
E. Hecht, 'Optics' (5th ed.), Ch.9 (Thin-film interference)
#薄膜干涉 #增透膜 #相消干涉
为什么肥皂泡表面会看到五颜六色的花纹？
Why do soap bubbles show colorful swirling patterns on their surface?
光照到肥皂膜上会在前后两个表面分别反射，这两束反射光发生干涉。由于膜的厚度不均匀，不同位置的光程差不同，有的波长被增强、有的被减弱，于是出现彩色条纹。随着水膜变薄，光程差持续变化，颜色也不断流动变换。
Light reflects from both the front and back surfaces of the thin soap film, and the two reflected beams interfere. Because the film thickness varies, the path difference differs from place to place, so some wavelengths are reinforced and others cancelled, producing colors. As the film thins, the path difference keeps changing and the colors keep shifting.
难度 进阶 · 适合 初中(12-15)
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（薄膜）
The Feynman Lectures on Physics, Vol. 1 (thin films)
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
#薄膜干涉 #光程差 #颜色
光那么直，为什么会绕过门缝边缘“散开”？
Light travels straight, so why does it spread out past a doorway edge?
这是衍射：当障碍或缝隙尺寸接近光波长时，波会绕到几何阴影里。单缝后放屏幕会看到中央亮纹加两侧明暗条纹。
This is diffraction: when an obstacle or slit is near the light's wavelength, the wave bends into the geometric shadow. A single slit casts a central bright band flanked by dimmer fringes.
难度 进阶 · 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》
The Feynman Lectures on Physics
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
#衍射 #波动 #波长
眼镜的镜片是怎么帮我们看清东西的？
How do eyeglass lenses help us see clearly?
近视或远视的眼睛把像聚焦错位置，镜片（凸透镜或凹透镜）提前弯曲光线，把焦点重新拉回视网膜上。
A defective eye focuses light at the wrong spot; a lens (convex or concave) bends the light first to move the focus back onto the retina.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-10-03 · 3 条独立证据
来源 · Source
Halliday、Resnick 与 Walker，《物理学基础》（第10版）
Halliday, Resnick & Walker, 'Fundamentals of Physics' (10th ed.)
独立核验依据 · Independent verification: 核验依据 2 angusrobertson.com.au
#透镜 #聚焦 #视力
海市蜃楼是怎么形成的？
How does a mirage form?
地面附近空气被晒得又热又稀，上层较密，光在密度渐变层中连续折射，把远处景物“弯”到眼前，看起来像水面倒影。
Hot, thin air near the ground bends light gradually toward denser upper air, curving distant images down to your eye so they look like a watery reflection.
难度 进阶 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-10-03 · 3 条独立证据
来源 · Source
Halliday、Resnick 与 Walker，《物理学基础》（第10版）
Halliday, Resnick & Walker, 'Fundamentals of Physics' (10th ed.)
独立核验依据 · Independent verification: 核验依据 2 angusrobertson.com.au
#海市蜃楼 #折射 #大气
光的多普勒效应与声音有什么不同？
How does the Doppler effect for light differ from that for sound?
声音的多普勒频移依赖观察者与介质的相对运动，而光在真空中只依赖光源与观察者的相对速度，且必须用狭义相对论修正。远离的光源波长被拉长呈红移，靠近则呈蓝移。
Sound's Doppler shift depends on motion relative to the medium, but light in vacuum depends only on the relative velocity of source and observer and needs relativistic correction. Receding light is redshifted to longer wavelength, approaching light blueshifted.
难度 进阶 · 适合 初中(12-15)
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。
多普勒 1842 年论文；爱因斯坦 1905 年狭义相对论
Doppler (1842); Einstein, special relativity (1905)
#多普勒效应 #红移 #相对论
全息底片上并没有物体的直接影像，为什么再现后能看到有纵深的立体像？它与普通照片的本质区别是什么？
A holographic plate holds no direct image of the object, so why does its reconstruction show a three-dimensional image with depth, and what is the essential difference from an ordinary photograph?
普通照相只记录光的强度分布，物体波的相位信息在曝光瞬间即告丢失，像因此缺乏纵深。全息术把物体散射波与一束相干参考光叠加，二者干涉形成的明暗条纹把相对相位编码进底片的强度图样中。再现时以同样的光照亮底片，条纹如同衍射光栅，重建出携带振幅与相位的原始波前，观察者看到的便是具有真实视差的立体像。
An ordinary photograph records only the intensity distribution of light; the phase of the object wave is lost at exposure, leaving the image without depth cues. Holography superposes the wave scattered by the object with a coherent reference beam, and the resulting interference fringes encode their relative phase into an intensity pattern on the plate. During reconstruction the same illumination turns the fringes into a diffraction grating that rebuilds the original wavefront with both amplitude and phase, giving the viewer an image with true parallax.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-11-04
来源 · Source
Gabor,《A New Microscopic Principle》,Nature,1948 (DOI: 10.1038/161777a0)
Gabor, 'A New Microscopic Principle', Nature, 1948, DOI: 10.1038/161777a0
独立核验依据 · Independent verification: 核验依据 1 Crossref DOI 10.1038/161777a0
#全息术 #波前重建 #光学干涉
光纤为什么能弯着传光?全反射有没有角度限制?
How does optical fiber guide light around bends — is total internal reflection angle-bound?
靠全反射:光从光密纤芯射向光疏包层,入射角大于临界角时能量全部折返;优质光纤的损耗可低至每公里约0.14分贝,但跨洋传输仍需每隔数十公里放大补偿。弯曲太急处局部入射角跌破临界值,光泄漏进包层衰减,故有最小弯曲半径。单模光纤芯径约9微米只容一个模式传播,消除多模色散;掺铒光纤放大器在玻璃里直接受激辐射放大,把中继站变成一段特殊光纤。全球九成以上的数据流量就跑在这些玻璃丝里。
Total internal reflection: light hitting the lower-index cladding above the critical angle reflects perfectly, with losses down to about 0.14 dB per kilometer — though trans-Pacific spans still need optical amplifiers every few tens of kilometers. Bends too tight drop local incidence below critical and light leaks out, hence minimum bend radii. Single-mode fiber shrinks cores to about nine micrometers so only one propagation mode survives, erasing modal dispersion; erbium-doped fiber amplifiers pump stimulated emission right inside the glass, turning repeaters into special fibers. Over ninety percent of global data traffic rides these threads.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-11-03
来源 · Source
Agrawal,《Fiber-Optic Communication Systems》第5版,Wiley,2021
G. P. Agrawal, Fiber-Optic Communication Systems, 5th ed., Wiley, 2021
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL21456153W：Fiber-Optic Communicat
#光纤 #全反射 #掺铒放大器
为什么镜子能照出我，而白墙不能？
Why can a mirror show me but a white wall can't?
镜子的表面非常平又亮，把光按规则方向整整齐齐弹回来，你的眼睛收到完整画面；白墙把光向四面八方乱反射，画面被打散，所以照不出像。
A mirror is smooth and shiny, bouncing light back in an orderly way to form your image; a white wall scatters light every which way, smearing the picture.
难度 入门 · 适合 幼儿(3-6)
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#光学 #反射 #镜子
肥皂泡上的彩虹色条纹是怎么来的？
How do the rainbow colors on a soap bubble form?
肥皂膜前后表面反射的光发生薄膜干涉：不同厚度的位置对特定波长满足相长或相消条件，于是出现随膜厚变化的彩色条纹。随着液膜重力变薄，颜色也不断流动变化。
Light reflected from the front and back surfaces of the soap film interferes. At each thickness certain wavelengths add and others cancel, producing colored bands that shift as gravity thins the film. This is thin-film interference.
难度 入门 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-11-03 · 2 条独立证据
来源 · Source
Born 与 Wolf《光学原理》；牛顿环实验
Born & Wolf, Principles of Optics; Newton's rings experiment
独立核验依据 · Independent verification: 核验依据 1 ISBN 9787121095146（豆瓣书目条目: 光学原理）；本条出处含多部著作，此标识只担保上面点名的这部 · 核验依据 2 OPENLIBRARY 标识 /works/OL717864W：Principles of optics（首版
#薄膜干涉 #肥皂泡 #光的反射
彩虹是怎么形成的？
How does a rainbow form?
雨后空气中有许多小水珠，阳光进入水珠后发生折射、反射和再次折射，不同颜色的光因折射角不同而分开，便形成七彩的彩虹。
After rain, tiny water droplets refract, reflect, and refract sunlight again; different colors bend by different amounts and separate, producing a seven-color rainbow.
难度 入门 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#彩虹 #折射 #色散
光的速度有多快？
How fast does light travel?
在真空中，光的传播速度约为每秒 30 万公里，是宇宙中已知的最快速度。光从太阳到地球大约只需要 8 分钟。
In a vacuum, light travels about 300,000 kilometers per second, the fastest speed known in the universe. Sunlight takes only about 8 minutes to reach Earth.
难度 入门 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#光速 #真空 #常数
为什么天上的星星会眨眼睛？
Why do stars appear to twinkle?
星光穿过地球动荡的大气层时，被不均匀的空气折射得忽明忽暗，看起来就像在眨眼。行星因为离得近、像个小圆盘，一般不眨。
Starlight is bent by turbulent air layers, making it flicker in brightness—twinkling. Nearby planets look like disks and usually don't twinkle.
难度 入门 · 适合 小学低段(6-8)
CC BY 4.0 · 已核验 · Verified 2026-10-03 · 3 条独立证据
来源 · Source
Halliday、Resnick 与 Walker，《物理学基础》（第10版）
Halliday, Resnick & Walker, 'Fundamentals of Physics' (10th ed.)
独立核验依据 · Independent verification: 核验依据 2 angusrobertson.com.au
#大气 #折射 #星星
肥皂泡表面五颜六色的条纹是怎么来的？
Where do the rainbow stripes on a soap bubble come from?
这是薄膜干涉：光线在肥皂膜的前后两个表面都反射，两束反射光因膜厚不同而走的光程不一样，某些波长相互增强、某些相互抵消，于是随厚度和视角变化显出彩色。膜越薄处颜色越淡，最薄时甚至呈现黑斑（两束光完全相消）。它和油膜、昆虫翅膀的虹彩是同一原理。
It is thin-film interference: light reflects off both the front and back surfaces of the soap film, and because the two beams travel different path lengths depending on film thickness, some wavelengths reinforce and others cancel. Colors shift with thickness and viewing angle; the thinnest spots even turn black where the beams fully cancel. Oil slicks and insect wings show the same effect.
难度 入门 · 适合 大众
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：著录仅给书名，无版次与年份；同一书名常对应多个版次，不臆测具体版本。
E. 赫克特《光学》第4版关于薄膜干涉的章节
E. Hecht, 'Optics' (4th ed.), chapter on thin-film interference
#薄膜干涉 #光的反射 #波长
什么是偏振光？
What is polarized light?
普通光波的电场在垂直于传播方向的各个方向上均匀振动，而偏振光的电场只沿某一固定方向振动。偏振太阳镜和液晶屏幕都利用了这一性质。它揭示了光作为横波的振动方向特征。
Ordinary light has its electric field vibrating uniformly in all directions perpendicular to travel, while polarized light has the field vibrating along one fixed direction. Polarized sunglasses and LCD screens exploit this. It reveals the transverse-wave directional character of light.
难度 入门 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#偏振 #横波 #电场
为什么雨后的彩虹往往出现不久就消失了？
Why does a rainbow after rain often appear only briefly and then vanish?
彩虹依赖空中悬浮的无数小水滴来折射分光，风或蒸发会让这些水滴很快消散或变大下落。一旦满足条件的水滴减少，彩虹就随之消失。
A rainbow depends on countless suspended droplets to refract and split light; wind or evaporation quickly disperses them or makes them fall. Once the right droplets thin out, the bow disappears.
难度 入门 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#折射 #水滴 #光学
彩虹为什么总是圆弧形的？
Why is a rainbow always an arc?
阳光在水滴里折射并反射，特定角度（约42°）的光最强；所有与该方向成固定夹角的水滴连成一个以反太阳点为中心的圆锥，地面截出圆弧。
Light refracts and reflects in droplets peaking at ~42°; all droplets at that angle from the antisolar point form a cone, and the ground cuts it into an arc.
难度 入门 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#光学 #彩虹 #折射
雨后天空为什么会出现彩虹？
Why does a rainbow appear after rain?
阳光穿过空中的小水珠，被折射、反射再折射出来，不同颜色弯折程度不同就分开了。背对太阳、看向带水珠的天空，就能看到弧形彩带。
Sunlight passing through tiny raindrops is refracted, reflected, then refracted again; colors bend by different amounts and separate. With the Sun behind you and mist ahead, you see an arched band of color.
难度 入门 · 适合 幼儿(3-6)
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#彩虹 #折射 #色散
什么是光的色散？
What is dispersion of light?
色散指不同频率的光在同一介质中折射率不同，因而偏折角度不同。棱镜把白光分解成七彩光谱，正是因为各色光速度略有差异。它是彩虹和分光镜背后的原理。
Dispersion means different light frequencies have different refractive indices in the same medium and thus bend by different angles. A prism splits white light into a spectrum precisely because each color travels at a slightly different speed. It is the principle behind rainbows and spectrometers.
难度 入门 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#色散 #折射率 #棱镜
为什么彩虹总是弯成一道弧，而且颜色顺序是固定的？
Why is a rainbow always a curved arc with a fixed color order?
阳光在水滴里折射、反射再折射，不同颜色因折射率不同而分开。观察者、太阳和水滴满足固定几何关系，彩虹总是出现在以反太阳点为中心的42度弧上，红在外紫在内。
Sunlight refracts, reflects, and refracts again inside droplets, separating colors by their different refractive indices. The geometry fixes the bow as a 42-degree arc centered on the antisolar point, with red outside and violet inside.
难度 入门 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#折射 #色散 #光学
为什么平面镜能照出左右相反的人像？
Why does a flat mirror show an image that is reversed left to right?
镜子实际是前后（沿法线方向）反转，并不是真正左右颠倒。因为我们用转过身来想象对面的人，才感觉左右互换，本质上镜像与实物关于镜面对称。
A mirror actually reverses front and back along the normal, not left and right. We perceive a left-right swap because we imagine the person turned around to face us; in truth the image is symmetric to you about the mirror plane.
难度 入门 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#反射 #镜像 #光学
镜子为什么左右颠倒，却不让上下颠倒？
Why does a mirror swap left and right but not up and down?
镜子其实只把前后翻转：它把朝里的方向反过来，不改变上下。我们觉得“左右颠倒”，是因为人习惯转身面对面，把前后反转变为左右的反向。
A mirror only flips front and back; it leaves up and down alone. We read it as left-right reversed because we imagine turning around to face the reflection, which turns the front-back flip into a left-right one.
难度 入门 · 适合 大众
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：著录仅给书名，无版次与年份；同一书名常对应多个版次，不臆测具体版本。
Eugene Hecht 著《Optics》（光学）
Eugene Hecht, Optics
#镜像 #反射 #对称
为什么雾天或瀑布边有时能看到没有颜色的白彩虹？
Why can you sometimes see a colorless white rainbow, a fogbow, in mist or near waterfalls?
雾滴比雨滴小得多，对光的衍射作用明显，把本该分开的色带重新糊在一起，颜色被冲淡。于是只看到一道柔和的白色或淡色弧，称为雾虹。
Fog droplets are much smaller than raindrops, and their strong diffraction smears the separated color bands back together, washing out the hues. The result is a soft white or faintly colored arc called a fogbow.
难度 入门 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#衍射 #散射 #光学
透镜为什么能把光线汇聚成清晰的像？
Why can a lens focus light into a sharp image?
透镜利用不同介质界面上的折射，使偏离主轴的光线弯折后交于一点（焦点）。凸透镜的曲率让平行入射光向中心偏折，从而把远处物体成像在焦平面附近。
A lens uses refraction at its curved surfaces to bend off-axis rays so they meet at a point (the focus). A convex lens curves parallel incoming light toward the center, forming an image of a distant object near its focal plane.
难度 入门 · 适合 大众
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：著录仅给书名，无版次与年份；同一书名常对应多个版次，不臆测具体版本。
Hecht《光学》
Hecht, Optics
#折射 #透镜 #焦点
把光盘斜对着灯光转动，为什么表面会出现一圈圈彩虹般的条纹？
Why do rainbow-like bands appear on a CD surface when you tilt it toward a light?
光盘表面布满了极密的同心沟槽，它们像光栅一样让不同波长的光朝不同方向偏折。这种衍射把白光按颜色分开，于是肉眼看到一圈圈彩纹。沟槽越密，色散越明显。
A CD's surface is covered with extremely fine concentric grooves that act like a diffraction grating, bending different wavelengths in different directions. The diffraction separates white light into colors, producing the rainbow bands you see. The finer the grooves, the more pronounced the effect.
难度 入门 · 适合 小学低段(6-8)
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：著录仅给书名，无版次与年份；同一书名常对应多个版次，不臆测具体版本。
E. Hecht,《Optics》(第5版),第10章(衍射光栅)
E. Hecht, 'Optics' (5th ed.), Ch.10 (Diffraction gratings)
#衍射光栅 #光盘 #干涉色
为什么同一根杆子的影子在早晨和傍晚很长，中午却很短？
Why is the shadow of a pole long in the morning and evening but short at noon?
影子长度取决于太阳高度角：太阳越低，光线越斜，影子被拉得越长；正午太阳接近头顶，光线近乎垂直，影子最短。这是地球自转造成的太阳角度变化。
Shadow length depends on the sun's elevation: the lower the sun, the more slanted the light and the longer the shadow; at noon the sun is near overhead so light is nearly vertical and the shadow is shortest. This comes from Earth's rotation changing the sun's angle.
难度 入门 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#影子 #太阳角度 #光学
为什么筷子插进水里看起来折断了？
Why does a chopstick look bent in water?
光从水进入空气时速度改变、方向弯折（折射），你眼睛沿直线回溯光线，便以为筷子在折断处换了方向，其实它没断。
Light bends (refracts) changing speed from water to air; your eye traces it straight back and sees a kink, though the stick is unbroken.
难度 入门 · 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
钟锡华,《现代光学基础》,北京大学出版社,2003
Zhong Xihua, Modern Optics Foundations, Peking University Press, 2003
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787301064634（豆瓣书目条目: 现代光学基础）
#光学 #折射 #视折
钻石在灯光下为什么会闪出五颜六色的小火花，而玻璃一般没有这种“火彩”？
Why does a diamond flash colored sparks under light while ordinary glass usually does not show such 'fire'?
不同颜色的光在钻石里折射程度不同，这种“色散”把白光拆成彩色的光。钻石的色散特别强，再加上高折射率让光在内部多次反射后从顶部射出，于是呈现出鲜艳的火彩。玻璃的色散弱得多，所以很少出现这种效果。
Different colors of light refract by different amounts, and this dispersion splits white light into colors. Diamond has unusually strong dispersion, and its high refractive index makes light bounce around inside before leaving through the top, producing vivid fire. Ordinary glass disperses far less, so the effect is weak.
难度 入门 · 适合 小学低段(6-8)
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：著录仅给书名，无版次与年份；同一书名常对应多个版次，不臆测具体版本。
E. Hecht,《Optics》(第5版),第3章(折射与色散)
E. Hecht, 'Optics' (5th ed.), Ch.3 (Refraction and dispersion)
#色散 #折射率 #钻石火彩
绿色激光笔射出的532纳米绿光并非直接来自激光管，那它究竟是怎样从红外光一步步变出来的？
The 532-nm green beam of a laser pointer does not come straight out of the laser diode, so how is it actually produced step by step from infrared light?
靠非线性晶体中的二次谐波产生。激光足够强时介质响应偏离线性，极化强度中出现正比于电场平方的项，它以两倍的频率振荡，辐射出频率加倍的光。只有无中心反演对称的晶体（如KTP）才有这一阶非线性；再经相位匹配让基频与倍频光同步积累，转换效率才高。绿光笔中1064纳米的红外光穿过KTP晶体便变成532纳米绿光。
Through second-harmonic generation in a nonlinear crystal. Once the light is intense enough, the medium's response leaves the linear regime: the induced polarization gains a term proportional to the square of the field, which oscillates at twice the frequency and radiates light at exactly double the frequency. Only crystals without inversion symmetry, such as KTP, show this second-order response, and efficient conversion further demands phase matching, which keeps fundamental and second harmonic in step as they build up. Inside a green pointer, 1064-nm infrared light passing through a KTP crystal emerges as 532-nm green.
难度 入门 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-11-03
来源 · Source
P. A. Franken et al.,Generation of optical harmonics,Physical Review Letters,1961
P. A. Franken et al., Generation of optical harmonics, Physical Review Letters, 1961
独立核验依据 · Independent verification: 核验依据 1 INSPIRE 标识 10.1103/PhysRevLett.7.118：Generation of Optic
#非线性光学 #二次谐波 #倍频