How many nanoseconds does it take light to travel a distance of 6.40 km in vacuum?

Answer;

= 21333 Nanoseconds

Explanation;

Distance = Speed x Time  

S = V x T  

( Here S = 6.40 km = 6400 m, V = 300000000 m/s, T = ?)  

6400 = 300000000 x T  

6400 / 300000000 = T  

=> T = 0.000021333 seconds

Convert seconds to nanoseconds  

1 second = 1000000000 nanoseconds  

Therefore,

T = 0.000021333 x 1000000000 nanoseconds  

T = 21333 Nanoseconds