Introduction to Physics: HCV Part 1

Chapter 1: Introduction to Physics

Short Answers:

1) The speed of light in vacuum is 299,792,458 m/s. Then time taken by light to cover a distance of 1 metre in vacuum = 1 / 299,792,458 s.
Hence, the metre is defined as the distance travelled by light in 1 / 299,792,458 s.
As 300,000,000 m/s is an approximate speed of light in vacuum, it cannot be used to define the metre.
The distance travelled by light in one second is 299,792,458 m. This is a large quantity and cannot be used as a base unit. So, the metre is not defined in terms of second.