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Overview
Diffraction is a wave behavior in which waves bend or spread when they encounter an obstacle, edge, or opening. It occurs with sound, water waves, light, radio waves, and other wave types. Diffraction becomes especially noticeable when the opening or obstacle is comparable in size to the wavelength.
Wave Spreading
When a wave passes through a narrow opening, it can spread out on the other side. The amount of spreading depends on the wavelength compared with the size of the opening.
Edges and Obstacles
Waves can bend around edges and obstacles. Long-wavelength waves diffract more strongly around ordinary objects than short-wavelength waves.
Single-Slit Diffraction
When light passes through a narrow slit, it can form a pattern of bright and dark regions. This pattern shows that light behaves as a wave.
Diffraction and Interference
Diffraction patterns often involve interference among wavelets from different parts of an opening. Bright regions come from constructive interference, while dark regions come from destructive interference.
Sound Diffraction
Sound can diffract around corners and through doorways. This is why a person can often hear sound from a source they cannot directly see.
Light Diffraction
Light diffracts, but the effect is often small in everyday situations because visible wavelengths are very short compared with most objects and openings.
Diffraction and Resolution
Diffraction limits the ability of optical instruments to distinguish fine details. Telescopes, microscopes, and cameras all face diffraction limits.
Applications
Diffraction is important in optics, spectroscopy, X-ray crystallography, acoustics, radio communication, imaging, microscopy, and wave analysis.
Common Mistakes
A common mistake is treating diffraction as a failure of straight-line travel only. Diffraction is a normal wave behavior and becomes stronger under specific wavelength-size conditions.
Why This Matters in Physics
Diffraction provides strong evidence for wave behavior and connects optics, sound, imaging, interference, and scientific measurement.