I have often stated in postulating my theories 
about the IR environment of night-flying moths, 
we are dealing with a region where light acts 
like radio and radio like light, Emphasis is 
added to my comparison by the use that 
present-day infrared technologists make not 
only of optics--refraction and reflection tech- 
niques--but also of radio techniques--wave- 
guide and resonant cavities--to detect such 
radiation. 
IR radiation has definite characteristics that 
make it useful for detection purposes (Hack- 
forth 1960), IR systems, lighter, smaller, and 
less complex than conventional radar systems, 
do not generate the detrimental side lobes of 
radar. One great advantage of an IR system is 
that it is passive and requires no transmitter 
to obtain the return signal, In other words, it 
senses the object directly. These advantages 
are pointed out for the obvious reason that 
when location is concerned, the efficiency is 
indisputable whether or not such a detection 
system were to be utilized by man to detect 



Energy and Luminosity(Arbitrary Units) 
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PSE SINS 
Fa ee 
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rockets or is a facet of nature itself in the 
marvelous intricacies of insect life. 
There is no doubt that moths are attracted 
to electromagnetic radiation. We are all fa- 
miliar with the moths' propensity for the 
ordinary 60-watt incandescent lamp. Figure 1 
gives the energy curve for such atransmitter, 
It is my contention that we have as much right 
to insist that the moth is attracted by the much 
greater energy of the longer wave IR output (a) 
as we have to insist that it is attracted by the 
lesser energy of the shorter wavelengths in 
the small visible area of the luminosity curve 
(b). 
It is well known that the higher temperatures 
produce shorter wavelengths (light) and that 
A max, displaces toward the longer and longer 
wavelengths as power and heat are reduced 
(fig. 2), This displacement becomes obvious 
when we hook a 60-watt tungsten lamp to a 
rheostat and reduce power. The visible spec- 
trum shifts from white to red heat and finally 
to black heat as the filament ''goes out,'' no 








Figure 1,--Spectral energy curve (a) and luminosity curve (b) of tungsten filament 
at 2200°K, (after Schilling 1940), 
157 
