# Quantum

August 3rd Fact-of-the-DayAn observable quantity
is said to be quantized if its magnitude is restricted to a discrete
set of values throughout at least part of its magnitude range. If the
magnitude of a quantity is always a multiple of a fixed unit, the unit
is called the quantum of the quantity. For example, when an analog audio
signal is digitized to allow transmission via an Internet media stream
the digitized audio signal can have magnitude values only at fixed multiples
of a step value, so the step unit is a quantum of the digitized audio
quantity. The magnitudes of many things that are commonly thought to exist
in a continuous (*analog*) range of magnitudes are, in fact, restricted
to multiples of a quantum. Electromagnetic radiation is an example. Electromagnetic
radiation cannot exist at any arbitrary energy magnitude. It can exist
only at discrete energy magnitudes that depend on the frequency. The quantum
of energy of electromagnetic radiation of frequency v is hv, where h is
Planck's constant. *©2005 Martek International All rights reserved.*

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