General Information (F-H)

Fermium — Fermium is a man made, radioactive metal element with the symbol Fm. It is named after Enrico Fermi.

Ferrites — Ferrites are a class of chemical compounds having the general formulae MFe2O4, where M is a divalent metal. Certain of these compounds are ferromagnetic, and possess in addition other properties which render them valuable for use in electric circuit components operating at high frequencies.

Ferrochrome — Ferrochrome is various alloys of iron and chromium employed in the manufacture of steel.

Ferromagnetic — Ferromagnetic is a term applied to materials such as iron, cobalt, nickel and certain alloys, which have a magnetic permeability very much greater than unity and which varies with the strength of the applied field.

Ferrous — Ferrous is a chemistry term referring to materials which contain iron.

Fibre Optics — Fibre Optics is a technology using light as a digital information bearer. Fibre optic cables ( light guides ) are a direct replacement for conventional wire, coaxial cable and many forms of radio, including microwave. Fibre optic lines actually cost less, occupy less space and provided far more transmission capacity than earlier methods, while providing superior quality due to virtual immunity to electrical interference.

Fluorescence — Fluorescence is the process of emission of electromagnetic radiation resulting from the absorption of certain types of energy.

Fluoride — Fluoride is the salt of hydrofluoric acid.

Fluorine — Fluorine is a gaseous element with the symbol F belonging to the group known as halogens. It is the most chemically reactive element (many substances ignite spontaneously in it), and for this reason it is never found uncombined.

Fluorocarbon — A fluorocarbon is a compound in which hydrogen atoms of a hydrocarbon have been replaced with fluorine.

Gamma Rays — Gamma Rays are a short, intense burst of electromagnetic radiation emitted by an unstable nucleus of radioactive material. Gamma rays have no electrical charge and can penetrate even thick lead and concrete.

Geode — A geode is a round hollow nodule containing earthy matters, sometimes quartz, sometimes agate. Geodes are found in most volcanic rocks and are formed by water depositing materials in the hollows of these rocks.

Geophagism — Geophagism is the practice of eating some kind of earthy matter, such as rock or chalk. It is most common amongst non-industrialised races, and was once thought to allay hunger. However, new evidence suggests that some peoples obtain valuable minerals in their diet from geophagism, as those minerals are not available in their normal food.

Glacier — In geography, a glacier is a massive crystalline block of ice or snow. They are found in regions of perpetual snow.

Glass — Glass is a brittle substance made by fusing silica, an alkali and a base.

Gravity — Gravity is the force of attraction between two objects resulting from their mass.

Hydrocarbon — A hydrocarbon is a chemical containing only hydrogen and carbon.

Hydrocarbons — see "hydrocarbon"

Hydrochlorothiazide — Hydrochlorothiazide is an antihypertensive and diuretic drug used to controls, but not cure high, high blood pressure and reduce fluid retention (edema). It works by forcing sodium and water excretion, thereby reducing the body fluid.

Hydrogen — Hydrogen is a gaseous element with the symbol H.

Hydroxide — A hydroxide is an inorganic compound containing one or more hydroxyl groups.