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Longer-wavelength radiation such as visible light is nonionizing; the photons do not have sufficient energy to ionize atoms. Throughout most of the electromagnetic spectrum, spectroscopy can be used to separate waves of different frequencies, so that the intensity of the radiation can be measured as a function of frequency or wavelength.
White light is dispersed by a glass prism into the colors of the visible spectrum. The visible spectrum is the band of the electromagnetic spectrum that is visible to the human eye. Electromagnetic radiation in this range of wavelengths is called visible light (or simply light).
Wavelength is a characteristic of both traveling waves and standing waves, as well as other spatial wave patterns. [3] [4] The inverse of the wavelength is called the spatial frequency. Wavelength is commonly designated by the Greek letter lambda (λ). For a modulated wave, wavelength may refer to the carrier wavelength of the signal.
Natural sources produce EM radiation across the spectrum. EM radiation with a wavelength between approximately 400 nm and 700 nm is directly detected by the human eye and perceived as visible light. Other wavelengths, especially nearby infrared (longer than 700 nm) and ultraviolet (shorter than 400 nm) are also sometimes referred to as light.
When a beam of light crosses the boundary between a vacuum and another medium, or between two different media, the wavelength of the light changes, but the frequency remains constant. If the beam of light is not orthogonal (or rather normal) to the boundary, the change in wavelength results in a change in the direction of the beam.
A clear daytime sky, looking toward the zenith. Earth's atmosphere scatters short-wavelength light more efficiently than that of longer wavelengths. Because its wavelengths are shorter, blue light is more strongly scattered than the longer-wavelength lights, red or green.
The rated wavelength is the peak wavelength that the LEDs put out, but light at both higher and lower wavelengths are present. [ citation needed ] The cheaper and more common 395 nm UV LEDs are much closer to the visible spectrum, and give off a purple color.
Comparison of sizes of semiconductor manufacturing process nodes with some microscopic objects and visible light wavelengths. At this scale, the width of a human hair is about 10 times that of the image. [70] To help compare different orders of magnitude this section lists lengths between 10 −8 and 10 −7 m (10 nm and 100 nm).