Speed of light in vacuum is:

Explanation

1. Light can be described as an electromagnetic wave
2. It does not require any material as a medium to propagate.
3. So it can travel through vacuum.
4. The speed of light is maximum in the vacuum and is denoted by $c$.
5. The maximum speed of light in S.I unit is $c=3\times {10}^{8}m/s$.

Hence, the speed of light in vacuum is $3\times {10}^{8}m/s$.