Etalon

[eyt-l-on] /ˈeɪt lˌɒn/

noun, Optics.
1.
an interferometer consisting of two glass plates that reflect approximately half of each ray of light incident upon them and that are separated by a small, fixed distance: used to compare wavelengths and to study atomic spectra.
/ˈɛtəˌlɒn/
noun
1.
(physics) a device used in spectroscopy to measure wavelengths by interference effects produced by multiple reflections between parallel half-silvered glass or quartz plates

Read Also:

Etam
eyrie. (1.) A village of the tribe of Simeon (1 Chr. 4:32). Into some cleft (“top,” A.V.,; R.V., “cleft”) of a rock here Samson retired after his slaughter of the Philistines (Judg. 15:8, 11). It was a natural stronghold. It has been identified with Beit ‘Atab, west of Bethlehem, near Zorah and Eshtaol. On the […]
Eta-meson
noun, Physics. 1. a neutral meson with strangeness 0 that is its own antiparticle. Symbol: η.
Etamine
[et-uh-meen] /ˈɛt əˌmin/ noun 1. a lightweight cotton or worsted fabric constructed in plain weave and loosely woven. /ˈɛtəˌmiːn/ noun 1. a cotton or worsted fabric of loose weave, used for clothing, curtains, etc

Etaoin-shrdlu
[et-ee-oin shurd-loo, -oh-in, ee-tee-] /ˈɛt iˌɔɪn ˈʃɜrd lu, -ˌoʊ ɪn, ˈi ti-/ noun 1. the letters produced by running the finger down the first two vertical rows of keys at the left of the keyboard of a Linotype machine: used as a temporary marking slug or to indicate that an earlier mistake in the line […]
Etape
[ey-tap; French ey-tap] /eɪˈtæp; French eɪˈtap/ noun, plural étapes [ey-taps; French ey-tap] /eɪˈtæps; French eɪˈtap/ (Show IPA). Military. 1. a place where troops camp after a day’s march. 2. a day’s march. 3. Archaic. supplies issued to troops during a march.