närfältsregionen

The närfältsregionen, often translated as the near-field region, is a concept used in physics, particularly in electromagnetism and acoustics, to describe the area close to a radiating source. It is contrasted with the far-field region, which is the area significantly distant from the source. The characteristics of waves and their propagation behave differently in these two regions.

In the context of electromagnetism, the near-field region is where the electric and magnetic fields are strongly coupled and their behavior is complex and dependent on the source's geometry and composition. Energy can be exchanged between the source and the near-field without necessarily radiating away as electromagnetic waves. This region is important for understanding phenomena such as antenna coupling and induction.

For acoustic waves, the near-field region is where the pressure and velocity components of the wave are not necessarily in phase and the acoustic impedance of the medium is not the dominant factor. The sound pressure level can decrease rapidly with distance in this region. Understanding the near-field is crucial for applications like acoustic imaging and the design of sound sources.

The transition between the near-field and far-field is not always sharply defined and depends on the wavelength of the radiation and the dimensions of the source. Generally, the near-field is considered to extend to a distance of about one wavelength or the source's diameter, whichever is larger, though specific definitions can vary depending on the discipline and the application.