noun. a grey tetravalent metallic element that resembles zirconium chemically and is found in zirconium minerals; used in filaments for its ready emission of electrons.
noun. 3 to 30 megahertz.
1. Noun, singular or mass The energy (E) of a photon is related to Planck's constant and the photon's frequency (f) by the equation E = hf.
