Visible light waves, spectrum

Ultraviolet radiation in industry may be found aronnd electrical arcs, and such arcs should be shielded by materials opaque to the ultraviolet The fact that a material may be opaque to ultraviolet has no relation to its opacity to other parts of the spectrum. Ordinary window glass, for instance, is almost completely opaque to the ultraviolet in snnlight at the same time, it is transparent to the visible light waves. A piece of plastic, dyed a deep red-violet, may be almost entirely opaque in the visible part of the spectrum and transparent in the near-nltraviolet. Electric welding arcs and... 

CONTINUUM THERMAL RADIATION Radiation which involves the transfer of heat by electromagnetic waves, confined to the relatively narrow window of the electromagnetic spectrum (i.e. visible light around 400 nm to infrared light around 1000 nm). The hot particles in and above hrework flames contribute to this type of radiation. 

Although they appear quite different to our senses, visible light, infrared radiation, microwaves, radio waves, X rays, and other forms of radiant energy are all different kinds of electromagnetic radiation. Collectively, they make up the electromagnetic spectrum, shown in Figure 5.3. 

Light is a part of the electromagnetic spectrum, which is more familiar than one might think. In addition to visible light, the electromagnetic spectrum includes radio waves, microwaves, infrared, ultraviolet, and X-rays. The only part of the electromagnetic spectrum detectable to humans is visible light. 

Since the atmosphere shields us from most deep ultraviolet radiation and from infrared radiation, the bulk of visible light (the solar spectrum) ranges from 350 to 750 nm. The 25,000 Frauenhofer15 "dark" lines are interruptions (in the range 295 to 1000 nm) in the continuous solar emission spectrum, due to absorption by the chemical elements present in the sun s atmosphere. Ultraviolet radiation was discovered by Ritter16 in 1801. Some radio waves do penetrate the earth s atmosphere, and they are most intense during solar storms. Infrared radiation also penetrates to some extent. 

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