Question

$\text{1 metre}$ can be defined as the distance travelled by light in in vacuum.

• A. $\frac{1}{3\times {10}^6}s$
• B. $\frac{1}{3\times {10}^8}s$
• C. $\frac{1}{8\times {10}^3}s$

Answer 1

The correct option is B $\frac{1}{3\times {10}^8}s$

The speed of light is constant in the vacuum. Hence, it is a suitable standard and can be taken as reference for measurement of distance. The speed of light is $3\times {10}^{8}m{s}^{-1}$ in vacuum.
We know, $speed=\frac{distance}{time}\Rightarrow time=\frac{distance}{speed}$
Given, distance $=1m$
$\therefore time=\frac{1}{3\times {10}^8}s$
i.e., One meter is the distance travelled by light in $\frac{1}{3\times {10}^8}s$ in vacuum.