Question

Which of the following is the most suitable standard for measurement of length?

• 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. For example, if we take a rod as a standard, then it might contract during winters or expand in summers. In case of a foot, it varies from person to person, so it is not a suitable option. But, the speed of light is constant throughout the universe; hence it is a suitable standard.

Meter is defined as the distance travelled by light in $\frac{1}{299,792,458}$ seconds in vacuum.