Spectrum, electromagnetic, illustrative chart

The spectral resolution of the most monochromatic laser yet devised, expressed as frequency of the laser emission divided by the laser linewidth, is approximately 5 x 10. The laser in question is a special-purpose He-Ne laser with a nominal wavelength of 632.8 nm (15,308 cm l or 4.74 x 10 Hz in frequency units) and a linewidth of 7 to 10 Hz. It is difficult to grasp the physical significance of this degree of resolution. One illustration is that, if the spectrum of this laser were displayed on chart paper such that the zero of electromagnetic energy were located at the sun and 15,308 cm l were located at the orbit of Earth, the width of the peak representing the output of the laser would be 3 millimeters. 

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