Linjalähde

A linjalähde, literally meaning "line source" in Finnish, is a conceptual term used in certain fields to describe a source of energy, radiation, or a physical phenomenon that is spread out along a line rather than concentrated at a single point. This contrasts with a point source, which is idealized as being located at a single point in space.

In physics, a linjalähde might represent a long, thin heated wire emitting thermal radiation or a linear antenna radiating electromagnetic waves. The mathematical description of the field produced by a linjalähde differs from that of a point source, often involving integrals over the length of the line. The intensity of the phenomenon typically decreases with distance from the line, but the rate of decrease is generally slower than that for a point source.

The concept of a linjalähde is also relevant in fields like environmental science, for instance, when modeling pollution plumes originating from a linear source such as a road or a long industrial exhaust pipe. In geophysics, it can be used to represent seismic sources or geological features that extend over a significant distance. The practical application of the linjalähde model depends on whether the linear dimension of the actual source is significantly larger than the distance at which its effects are being observed.