direction measurement
21century — 1. a unit of quantity equal to 100. In ancient Rome, a century was originally a company of about 100 soldiers led by an officer called a centurion. 2. a traditional unit of time equal to 100 years. In naming centuries, historians recall… …
22color units — several systems have been devised to measure colors. For most of us not directly concerned with dyes, paints, or inks, the subject was academic until recently, but now computers require precise methods for describing the colors to be displayed …
23dB i — a unit measuring the gain of an antenna. The reference level is the strength of the signal that would be transmitted by an isotropic antenna: one radiating equally in all directions. For example, an antenna rated 20 dB i transmits a signal in… …
24degree Fahrenheit — (°F) a traditional unit of temperature still used customarily in the United States. The unit was defined by the German physicist Daniel G. Fahrenheit (1686 1736), who also invented the mercury thermometer. Fahrenheit set 0° at the coldest… …
25joule — (J) the SI unit of work or energy, defined to be the work done by a force of one newton acting to move an object through a distance of one meter in the direction in which the force is applied. Equivalently, since kinetic energy is one half the …
26line — 1. (li or ) a traditional unit of distance equal to 1/12 inch (about 2.1167 millimeters). For measuring the thickness of buttons, there is also a smaller line equal to 1/40 inch (0.635 millimeter). The line is called the ligne (see… …
27phi unit — a logarithmic unit used to measure grain sizes for sand, grit, and gravel. The 0 point of the scale is a grain size of 1 millimeter, and each increase of 1 in the phi number corresponds to a decrease in grain size by a factor of 1/2. Thus 1… …
28photon — 1. a quantum of light energy, or, more generally, of any form of electromagnetic energy having a single wavelength, direction, and polarization. 2. a former name for the unit of retinal illuminance now called the troland …
29point — (pt) 1. a unit of angle measure equal to 1/32 of a circle. Compasses are read by suspending the compass needle over a compass card traditionally inscribed with a 32 point star. Each point of the star represents a named direction; for example,… …
30var — a unit of the reactive electric power delivered by an alternating current (AC) circuit. In an AC circuit, the electric potential or voltage (measured in volts) and the current (in amperes) alternate direction, varying smoothly according to… …
