Word: ultraviolet
(lookup in dictionary)
(lookup stats)
Dates: all
Sort By: most recent first
(reverse)
...biology is how to take a microscope picture of a healthy living cell. Most tissue cells, whether animal or vegetable, are transparent to ordinary light. To make them visible they must be stained, and the stain either kills them or sickens them. They can be seen with special ultraviolet microscopes, but strong ultraviolet is also deadly to cells; only the picture of a tiny corpse appears in the photomicrograph...
...Robert Barer of Oxford University, England, is sure he has licked the problem. He uses monochromatic (single wave length) ultraviolet at an intensity which is too low to hurt the cell. It is also too feeble to make a useful impression on a fluorescent screen or photographic plate, so Barer focuses the invisible image, enlarged with a reflecting microscope to about three inches in diameter, on a screen. Then, by means of a rapidly revolving mirror, he "scans"' the image, throwing the ultraviolet light from a narrow slice of it into a photomultiplier tube. The faint glimmer of ultraviolet...
Hour after hour, every day, hundreds of itchy victims trooped into the nine treatment centers set up by the city's brisk, go-getting health officer, Dr. Joseph Gimby. Each child's head was examined under a special ultraviolet lamp which makes infected areas show up fluorescent. Where the fungus* had a foothold, the patches were marked and, down the line, were clipped. Many boys and a few girls were completely shaved...
...much is known about its complex chemistry but Dr. Strehler points out an extraordinary fact. The light that comes from luciferin has been analyzed spectroscopically and turns out to be very similar to the fluorescent glow given off by riboflavin (vitamin B2) when it is irradiated with invisible ultraviolet...
...most laymen, the atmosphere on a clear day or night looks beautifully transparent. The astronomers, aware of this illusion, know that even the clearest atmosphere is opaque to many kinds of radiation. Visible light pushes through it without much loss. So do ultraviolet and infrared if their wave lengths are not very different from ordinary visible light. Most other radiation coming from outside the atmosphere is absorbed before it reaches the ground. The chief exception is radio waves, which penetrate not only the atmosphere but also thick clouds...