Question

define one metre length​

Answer 1

ANSWER

Since 1983, the metre has been internationally defined as the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second. ... By using a light source of known and stable wavelength, lengths up to 100 metres can be directly measured, with accuracies up to 1 part in a few million.

Answer 2

$\huge\red{ANSWER}$

A METRE LENGTH : The length of the path travelled by light in vacuum during a time interval of 1/299792458 of a second.

1 METRE = 1/1000 OF A KILOMETRE