Phosphoroscope

A phosphoroscope is piece of experimental equipment devised in 1857 by physicist A. E. Becquerel to measure how long it takes a phosphorescent material to stop glowing after it has been excited.

A sample of phosphorescent material is placed in between the two disks.

Light coming in through a hole in one of the discs excites the phosphorescent material which then emits light for a short amount of time.

The disks are then rotated and by changing their speed, the length of time the material glows can be determined.

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