Three-inch pieces of light.
Though light travels so fast that it can encircle the earth seven times in a second, the two physicists made use of a shutter that turned the light on and off with such rapidity that each "piece" of light was only about three inches in length. Each flash lasted a hundred billionth of a second.
The investigation was undertaken in an endeavor to measure the length of what are called "quanta" of light, for according to modern ideas, light is transmitted as separate pulses, each of which is called a quantum. Physicists have been uncertain as to how long these quanta are, but by some it was believed that they were as much as a yard in length.
These extremely short flashes of light were measured by a very delicate photoelectric cell, which gives off an electric current when illuminated, and they found that so long as the total amount of light reaching the cell was the same, the resulting current was not affected by the length of the individual flashes. One three inches long produced an effect as well as a piece of light many miles or more in length, and this shows, say the investigators, that the individual quanta are less than three inches in length.
|Printer friendly Cite/link Email Feedback|
|Title Annotation:||From the Archive; measuring light quantum|
|Article Type:||Brief article|
|Date:||Mar 24, 2012|
|Previous Article:||Pondering speedy neutrinos.|
|Next Article:||Photon size a trickier question today.|