Harmonic

The harmonic of a wave is wave whose frequency is an integer number of multiples of the fundamental frequency of the wave. For example, if the fundamental frequency is f, the harmonics are 2f, 3f, 4f, and so on.



Fundamental frequency, with first and second harmonics below.

1531 (implied in harmonical), from L. harmonicus, from Gk. harmonikos "harmonic, musical," from harmonia.

Hologram

An interference pattern that is recorded on a high-resolution plate, the two interfering beams formed by a coherent beam from a laser and light scattered by an object. After formation, if lit and viewed correctly, a 3-D image of the object is seen.

1949, coined by Hungarian-born British scientist Dennis Gabor, 1971 Nobel prize winner in physics for his work in holography, from Gk. holos "whole" (in sense of three-dimensional) + -gram. Holography "process of using holograms" coined 1964 from hologram on analogy of telegraphy/telegram.

Homogeneous

A property of substance that is the same in all directions.

1641, from M.L. homogeneus, from Gk. homogenes "of the same kind," from homos "same" + genos "kind, gender, race, stock."