Question

Define the following term:
- intensity

Answer 1

Intensity — a measure of the strength, magnitude or concentration of something.

Common senses and technical meanings:
- General/colloquial: the degree of force, energy, emotion or activity (e.g., “high intensity” exercise or emotion).
- Physics (waves / radiation): the power transmitted per unit area, i.e. energy per unit time crossing a unit area (SI unit W·m⁻²). For a simple source with power P uniformly over area A, I = P/A. Related technical terms:
- Radiant intensity: radiant power per unit solid angle (W·sr⁻¹).
- Luminous intensity: photometric analogue measured in candelas (cd = lumen·sr⁻¹).
- Acoustics: sound intensity = acoustic power per unit area (W·m⁻²); sound intensity level is often expressed in decibels.
- Imaging/digital: pixel intensity = brightness or gray-scale value of a pixel.
- Exercise physiology: effort level, often expressed as % of max heart rate or % of one-rep max.

Note: in many contexts “intensity” is distinct from amplitude or total energy — it describes strength per unit area, per unit solid angle, or per unit measure rather than an absolute total.