A Q. No. la sap
What is derived is one second time?
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The second (abbreviation, s or sec) is the Standard International ( SI ) unit of time. One second is the time that elapses during 9,192,631,770 (9.192631770 x 10 9 ) cycles of the radiation produced by the transition between two levels of the cesium 133 atom. ... One second is equal to 1/86,400 of a mean solar day.

Explanation:

the duration of a photographic flash is related to an rc time constant, which is 0.100 μs for a certain camera.

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