Tuesday, July 21, 2009

Observation permitted by laser light: 635 nM

The light-scattering properties of nano-particles of colloidal gold provide us with a blood-red solution (the color determined by the size of the particles) in which the metal is suspended. The absorption of light at specific wavelengths, combined with the careful manipulation of the solution, can allow us control the depths to which different lasers will penetrate the column.

There are interesting variations in the sensitivity curve of the human eye during different lighting scenarios. Very sensitive to yellow wavelengths, the eye will perceive a yellow laser (561 - 594nM) as brighter and more intense than a red one (630 - 650nM) of comparable power. In the fading light, the experience of these intensities will change as the numerous rod photo-receptors in the eyes become more active.
















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