Evening public ledger. [volume] (Philadelphia [Pa.]) 1914-1942, 1922-06-23

Let us suppose today that we have
invented perfectly marvellous instru.
ment---an instrument that there Is no
possibility of achieving in practice but
which is perfectly easy to establish in
an ordinary imagination.
This instrument is merely wire
string like the string Of a mandolin
or a guitar and so arranged that, by
twisting a key we can stretch 1t tighter
or loosen it without any limits. II we
ton at least, be no limit to the slow
ness or the rapidity with which we
could make it vibrate. And we must
imagine that, instead Of affecting the
air, the string makes vibrations In the
ether.
We know that IL we cause q million
waves q second to pass any given point
each Of these waves, from crest to
crest, would measure only one-millionth
the length Of waves passing at the
rate Of only a single one in second.
! We can, therefore, put it down as a
fact that the faster the vibrations are
the shorter the wave length will be.
Let us suppose that we are starting
our experiment with the string as loose
as we can possibly make It. That will,
Of course. give US the biggest wave
that wei can produce. Science has
made radio waves 35 900 meters long,
but they are not used for practical pur-
poses. Still, 1t Is possible to produce
them. Let us now gradually tighten
the string while We continue plucking
1t. When the string vibrates fast
enough to produce waves of 10000
meters, or more than five miles, from
crest to crest, we are getting into the
band of lengths used for commercial
purposes.
AS we tighten the string more and
more and shorten the length Of the
waves from crest to crest We get to
26OO meters, which is the length used
for sending out the time tick at noon
and 10 p. NJ; we tighten some more
and increase the rapidity Of vibration.
passing through the 600-meter wave of
the ordinary commercial station, then
the 800 meter wave Of the broadcasting
stations and the 200 meter wave used
by the amateurs.
So we can 90 on tightening until we
produce waves only about one foot
from crest to crest.
As we tighten from this point on we
come to curious phenomenon. We
come to a band Of wave lengths about
|
We must keep on tightening until the
waves which We produce are only about
one tenth Of an inch from crest to
tCrest.
Here we begin to be able to detect
them again but not by means Of any
electrical instrument. They have now
J become Of such length and frequency
; that the human body itself is conscious
of them. AS We continue to tighten
; the string. the hand in which we are
plucking it will, in imagination, tell
us what is happening. We are now
, producing waves which We know as
heat.
Continue to tighten the string
! thereby increasing the number of vi
brations and making the waves con,
tinually smaller and gradually we will
see the string beginning to glow. Herr
!, we have a curious overlapping of two o
, our senses Just as, in radio work, we'll
designed sets have large overlap
for their various coils.
This overlap is detected from our
string by the fact that our hand tells
us it is growing hotter and our eye
\ tells US It is beginning to glow.
We continue to tighten the string
, and soon it is blazing with pure
l white light. 1t IN incandescent. Th'
e longest waves that are both heat anc
9 light will produce red glow. Th'
I color red is caused by the longes
waves that are visible to the eye. ant
as we shorten the waves and thus in
n crease the number of vibrations W,
5 pass through orange and yellow ant
= green, blue and violet. The violet ray!