Distance covered by the light = 3.20 km = 3200 meter
speed of the light is [tex]c = 3* 10^8 m/s[/tex]
so here time to cover the given distance
[tex]t = \frac{d}{c}[/tex]
[tex]t = \frac{3200}{3*10^8}[/tex]
[tex]t = 1.067 * 10^{-5}s[/tex]
as we know that
[tex]1 ns = 10^{-9} s[/tex]
So the time tocover the distance in nanosecond unit is
[tex]t = 10670 ns[/tex]
