Actinometer

Part of speech: noun

Definitions

1. A measuring instrument that quantifies the intensity of radiative energy or light A device used to assess the strength of light across different wavelengths in experimental settings A tool employed to evaluate solar radiation intensity for research applications
2. An apparatus designed to determine the amount of radiant energy or light hitting a surface
3. An instrument that gauges the strength and power of light in various scientific experiments

Etymology: The word is built from two Greek elements that English took in separately. The first, "aktis" in ancient Greek, meant a ray of light or the spoke of a wheel, and it gives English the prefix "actino-", which carries the sense of radiation. The second element, "metron", meant a measure, and it came into English through French "-mètre" and then took the form "-meter". Put together, an actinometer is literally a measurer of rays. The combining form "actino-" is a modern scientific construction, drawn from classical Greek material, rather than a word anyone in antiquity used for a light-measuring device. Instruments of this kind were built to quantify the chemical or radiant effect of sunlight, which made a fresh compound from familiar roots the natural choice for naming them.