lähisusvahemik

Lähisusvahemik, often translated as near-field or close-range, refers to a region or area where interactions are primarily governed by proximity. This concept appears in various scientific and technical contexts, including physics, acoustics, and electromagnetics. In physics, it describes the domain close to a source or object where the field's characteristics are dominated by the source's immediate properties, as opposed to the far-field where the waves behave more predictably as plane waves.

In acoustics, the near-field is the region surrounding a sound source where the pressure and particle velocity are not in phase, leading to complex sound patterns. This contrasts with the far-field, where the sound behaves more like a propagating wave. Understanding the near-field is crucial for accurate acoustic measurements and for designing sound-producing devices.

Electromagnetically, the near-field is the region very close to an antenna or radiating source. Here, the electric and magnetic fields are strongly coupled and do not propagate as waves in the same way they do in the far-field. This near-field region is important for understanding antenna performance, particularly in applications like inductive charging or short-range wireless communication. The transition from near-field to far-field is generally considered to occur at a distance related to the wavelength of the radiation and the dimensions of the source.