波粒二象性Wave–particle duality

17 世纪牛顿支持光的微粒说，惠更斯支持波动说。1801 年杨的双缝干涉实验和 19 世纪麦克斯韦电磁理论确立了光的波动性。1905 年爱因斯坦用光量子 E = hν 解释光电效应，1923 年康普顿散射实验证明光子具有动量 p = h/λ，光又被确认具有粒子性。

In the seventeenth century Newton favoured a corpuscular theory of light and Huygens a wave theory. Young's double-slit experiment of 1801 and Maxwell's electromagnetic theory established light's wave nature, but in 1905 Einstein explained the photoelectric effect with light quanta, E = hν, and in 1923 Compton scattering showed photons carry momentum p = h/λ, confirming a particle nature too.

1924 年德布罗意提出物质粒子也具有波长 λ = h/p。1927 年戴维森和革末用镍单晶、G. P. 汤姆孙用金属薄膜观察到电子衍射，证实了物质波（戴维森与汤姆孙获 1937 年诺贝尔物理学奖）。后来中子衍射、原子干涉以及 1999 年 C₆₀ 分子的双缝干涉都被实验证实。

In 1924 de Broglie proposed that matter particles have a wavelength λ = h/p. In 1927 Davisson and Germer with a nickel crystal, and G. P. Thomson with metal foils, observed electron diffraction, confirming matter waves; Davisson and Thomson shared the 1937 Nobel Prize in Physics. Neutron diffraction, atom interferometry and, in 1999, double-slit interference of C₆₀ molecules followed.

1927 年玻尔提出互补原理：波动性和粒子性是互补的，不能在同一实验中同时完全显现。波粒二象性是量子力学的基石，直接催生了电子显微镜、中子衍射和原子钟等技术，也解释了为何电子在原子中只能处于特定的“驻波”状态，即量子化的轨道。

In 1927 Bohr formulated complementarity: wave and particle aspects are complementary and cannot both be fully displayed in one experiment. Duality is a cornerstone of quantum mechanics, underlying the electron microscope, neutron diffraction and atomic clocks, and it explains why electrons in atoms can occupy only particular standing-wave states, the quantised orbitals.