This example is in the Garland Collection of Classical Physics Apparatus
at Vanderbilt University. It was made by Duboscq of Paris, and is designed to
be mounted on a solar microscope.
|| Say "Becquerel" and the average physicist immediately thinks
of Henri Becquerel (1852-1909) who discovered the phenomenon of radioactivity
in 1896 while investigating the phosphorescence of uranium compounds. His
father, Alexandre-Edmond Becquerel (1820-1891) is best known for his work
on luminescence and phosphorescence; the scientific dynasty was established
by his grandfather A.C. Becquerel (1788-1878), who developed the differential
A-E Becquerel developed the phosphoro-
scope to measure the time between the excitation of the phosphorescent
material and the extinction of the glow. The sample is placed between two
rotating disks with a series of holes spaced at equal angles a given distance
out from the center. The holes in one disk do not line up with the holes
in the other disk. The crystal is excited by light coming in through one
hole, and viewed by the phosphorescent light coming out of the other hole.
Varying the speed of rotation makes it possible to measure the short time
interval during which the phosphorescent light is emitted.
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