Question

1 metre can be defined as:

• A. Distance travelled by light in (1/299792458) s
• B. A rod
• C. Foot of a person
• D. Either of the above

Answer 1

The correct option is A

Distance travelled by light in (1/299792458) s

A suitable standard of unit is one which does not change with time or place. Time taken by light to travel $299792458km$ in vacuum and speed at which light travels for $299792458km$ in vacuum will be a measure of time and speed respectively. For measuring the length, distance traveled by light in $\frac{1}{299792458}$ seconds is calculated.

Since, speed of light is constant throughout the universe, calculating distance from this equation will be the most suitable option.