Science & TechnologyGreek → English
Photometer
/foʊˈtɒmɪtər/noun
An instrument that measures the intensity of light.
The Greek roots
φῶς
phôs
light
μέτρον
métron
measure
Literally: “light measure”
The story of the word
Johann Heinrich Lambert's Photometria of 1760 turned the measurement of light into a science with laws attached, and the instruments inherited the name. Early ones ran on the eye: you slid a candle along a bar until two patches on a screen looked equally bright, which made the observer part of the apparatus. Photoelectric cells took over after 1900, and an astronomer's photometer now counts individual photons.
- How it travelled
- Ancient Greek → modern coinage → English
- First recorded
- 18th century
Same family
photographphosphorusphotonbarometer
In a sentence
The photometer logged a dip of one percent as the planet crossed the star.