1 If the invitation says black tie, women should wear a floor-length, evening gown. 2  A tuxedo is mandatory if you're a man. 3  This is your chance to dress as if you were headed to the Oscars. 4  Black tie optional means that wearing a tuxedo or long evening gown is not mandatory, but guests should feel free to do so.
Ether is an organic functional group consisting of a disubstituted oxygen, or an oxygen atom bonded to 2 carbon atoms (if adjacent to a ketone, functional group is then called an ester).
So the ether is a medium which goes through all objects, but some of it is trapped by transparent substances and whose elasticity depends on the color of light going through it. In order to test this Fizeau performed a very important experiment.aving postulated the existence of the ether as the medium in which light travels it becomes interesting to determine the properties of this material.