Question

The speed of light in air or vacuum is:

• A. $330m{s}^{-1}$
• B. $3\times {10}^{8}m{s}^{-1}$
• C. $30kmph$
• D. $100m{s}^{-1}$

Answer 1

The correct option is B

$3\times {10}^{8}m{s}^{-1}$

In vacuum, lights of different colours and wavelengths travel with the same speed, but they travel at different speeds in different media. The speed of light is $3\times {10}^{8}m{s}^{-1}$ in vacuum or air, $2.25\times {10}^{8}m{s}^{-1}$ in water and $2\times {10}^{8}m{s}^{-1}$ in glass.