Radical

3906

Radio

upon the temperature of the body. Both
theoretical and experimental investigations
have shown that through a great range of
temperature a given rough or black surface
will emit radiant energy at a rate propor-
tional to the fourth power of the absolute
temperature. For the more practical aspects
of electrical radiations, see ELECTROMAGNETIC
WAVES.

Radical, a term applied to a person, party,
or movement advocating extreme measures
directed towards political reform. In Great
Britain the Radicals counted among their
numbers such notables as James Mill, Joseph
Hume, Bentham, Grote, Ricardo, John Stuart
Mm, Thomas Paine, Bright, and Chamber-
lain. There has never been an organized
Radical Party in the United States.

Radicals, or Radicles, or Residues, are
unsaturated groups of atoms that pass un-
changed from compound to compound. Like
simple elements they have no separate ex-
istence. The instant of their liberation they
become satuiated compounds in either pair-
ing among themselves, or uniting with other
elements. Radicals are derived by removing
one or more atoms from certain saturated
compounds. For example, the —OH (hy-
droxyl) radical is theoretically derived by
removing one hydrogen atom from water
(HOH).

Radio. This term is decidedly general
although there is a tendency in some locali-
ties to use the word 'radio' as meaning spe-
cifically a radio receiver. 'Radio' covers the
entire field known as 'wireless,' which word
signifies all forms of communication of au-
dible and visible effects by means of electro-
static-electromagnetic waves, This article
merely classifies the fields of major import-
ance as to present-day use. It does not
consider the technical theory nor the details
of any equipment involved. For specific in-
formation covering the principles of opera-
tion and description of the apparatus refer
to articles on WIRELESS TELEPHONY and
WIRELESS TELEGRAPHY.

In a broad sense the source or the appara-
tus responsible for the production of these
electrostatic-electromagnetic waves is the
transmitter. Similarly the receiver consists
of the apparatus which intercepts these
waves and is responsible for the reproduction
of the original audible or visible effects which
occurred at the transmitter. The ultimate
effect at the receiver may be converted into
various indicative, signaling or recording re-

sults. As the electrostatic-electromagnetic
waves require no medium for their propaga-
tion there is no necessity for any fixed dis-
tance relationship between transmitter and
receiver. Furthermore a transmitter may
readily communicate with any number of
receivers simultaneously irrespective of
whether any individual receiver is stationary
or is in motion as on a train, automobile,
ship, airplane, etc. The entire long distance
radio communication art dates back to Dec.
12, 1901, when Marconi in Nova Scotia re-
ceived the first trans-oceanic radio message
from his station in England. Short wave
transmission and reception has been devel-
oped highly since its general adoption for
this work in 1924. Long wave communica-
tion, however, is widely used for long dis-
tance international telegraphy. Frequencies
in the band from 10,000 to 100,000 cycles
per second are employed, as this range has
proven to give the greatest degree of relia-
bility. More power is required than for short
waves to cover the same distance.

Radio service reports of weather and me-
teorological advices have been in regular op-
eration for quite some years. Storm warnings,
time signals, reports on menaces to navi-
gation such as icebergs, derelicts, etc., have
been of immense value to shipping and have
also been of benefit over the land. Market
reports together with timely advice in fields
such as agriculture are conducted by several
governments. There are press services for
the rapid transmission and distribution of
news. This applies to ships as well as shore
service. It makes possible the printing of an
up-to-date newspaper aboard ship, contain-
ing the latest news. Photography, maps,
charts, etc., have been reproduced over trans-
oceanic distances. It is possible to reprint
a newspaper at a distant point by photo
radio. In television, images in motion of the
objects focused at the transmitter are repro-
duced at the receiver. Sound effects may
be reproduced simultaneously over the regu-
lar broadcast system working in conjunc-
tion with the television apparatus, but they
are two separate and distinct transmitters
and receivers. See TELEVISION.

Radio Circuits and radio apparatus have
been used extensively for making various
types of measurements and tests in the in-
dustrial world. Furthermore, tubes and
speakers developed by the use of radio have
been commonly adapted to many other pur-
poses. Radio waves have been used in locat-