Compute the force on each of two electrons when they are seperated in vaccum by a distance corresponding to the approximate size of an atom(0.100nm)

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

answer(20) psi;

one "light year" is the distance that light travels, through vacuum, in one julian year.   that's 365.25 days, of 24 hours each.