intensitet

Intensitet is a term used across disciplines to describe the strength, magnitude, or energy density of a phenomenon. It denotes how strong or impactful something is, often relative to a reference quantity such as time, area, or perceived response. Because its precise meaning varies by field, the definition is context dependent.

In physics and engineering, intensity typically means energy flow per unit time per unit area. Radiant intensity is the power emitted per unit solid angle, while irradiance is the power arriving on a surface per unit area. In acoustics and optics, intensity describes how much energy is delivered to or through a given region and is related to perceived brightness or loudness.

In photometry, luminous intensity is the measure of perceived power per unit solid angle, adjusted for human eye sensitivity, and is measured in candelas. Higher intensity generally corresponds to brighter light or stronger sound, though perception depends on wavelength and environment.

In exercise science, intensity indicates the level of effort, often expressed as a percentage of maximum heart rate or VO2 max, or by subjective scales such as the Borg scale. In psychology and medicine, intensity can describe the strength of symptoms or stimuli, usually assessed with rating scales.

In music and the arts, intensity relates to dynamic level or expressive force, shaping how strongly a piece is performed.

Etymology: from Latin intensitas, meaning stretched or strained.