vågstråle

Vågstråle, literally translating to “wave beam” in Swedish, is a concept in wave physics describing a narrow, directed flow of wave energy along a preferred path. It applies to various wave types, including light, sound, and other mechanical or electromagnetic waves. A vågstråle arises when a source has a finite aperture or when multiple emitters are phased to produce constructive interference in a particular direction, concentrating energy within a limited angular range.

The energy distribution across a vågstråle is characterized by its beam width and its decline in intensity with distance, due to diffraction. In simple terms, a larger aperture or shorter wavelength yields a more collimated beam (smaller divergence), while diffraction imposes a fundamental limit on how narrow a beam can be. For many optical and acoustic cases, approximate relations such as the beam divergence theta ~ lambda/D (where lambda is wavelength and D is aperture size) describe this behavior.

Common methods to create and control vågstrålar include focusing elements like lenses and parabolic mirrors in optics, horn or dish antennas in radio waves, and phased-array systems in acoustics and ultrasound. These beams are central to applications such as laser scanning, optical communications, ultrasound imaging, sonar, and radar.

Related concepts include diffraction, wavefronts, coherence, polarization, and beamforming. In geophysics and seismology, ray theory uses analogous ideas to describe the path of high-frequency energy as it travels through media.