The double-slit interference experiment is a fundamental demonstration of light's wave nature. When coherent light passes through two closely spaced slits, each slit acts as a new wave source. These waves propagate and interfere with each other, creating alternating bright and dark fringes on a screen.
According to Huygens' principle, when a coherent light wave encounters the double slit, each slit acts as a new point source of spherical waves. These secondary wavelets spread out from each slit with the same frequency and maintain a constant phase relationship, making them coherent sources.
When waves from the two slits reach a point on the screen, they superpose according to their path difference. If the path difference equals an integer multiple of wavelength, constructive interference occurs creating bright fringes. If the path difference equals an odd multiple of half wavelength, destructive interference creates dark fringes.
双缝干涉实验是物理学史上最重要的实验之一。它首次直接证明了光具有波动性质。当光束通过两个平行的狭缝时，每个狭缝都会产生衍射现象，形成的两个光波会发生干涉，在屏幕上产生明暗相间的条纹图样。
实验装置相对简单。我们需要一个单色光源，发出相干光。光束照射到有两个平行狭缝的挡板上，缝间距用d表示。在距离双缝D的位置放置观察屏。这些参数决定了干涉条纹的特征。
当光通过两个狭缝时，每个缝都成为新的波源。从两个缝发出的光波到达屏幕上同一点时，会发生叠加。根据波的叠加原理，如果两波同相，振幅增强形成亮条纹；如果反相，振幅减弱形成暗条纹。关键在于光程差，它决定了两波的相位关系。
干涉条纹由明暗相间的条纹组成。中央是最亮的零级亮条纹，两侧对称分布着高级次亮条纹，亮度逐渐减弱。条纹间距由波长、缝间距和缝屏距离决定，遵循图中所示的公式。这种规律的条纹图样直接证明了光的波动性质。
双缝干涉实验不仅具有重要的历史意义，也为现代科学技术发展做出了巨大贡献。它首次直接证明了光的波动性质，奠定了波动光学的理论基础，并为后来量子力学的发展提供了重要启示。在现代技术中，干涉原理被广泛应用于精密测量、激光技术、全息摄影等领域，继续推动着科学技术的进步。
The double-slit interference experiment has profound significance in modern physics and technology. It established the wave nature of light and laid the foundation for wave optics. Today, interference principles are applied in precision measurement instruments, laser interferometry, holographic technology, and quantum optics research. This simple yet elegant experiment continues to inspire new discoveries in quantum mechanics and photonics.