Question

what is the speed of light?

Answer 1

The speed of light in vaccum, commonly denoted by c, is a universal physical constant in many areas of physics. The speed of light = 299 792 458 m/s.

Answer 2

Speed of light is not constant. It varies from one medium to another. For example, light's speed in air is different from its speed in water.

Speed in Vacuum(or air) = 3×10⁸ m/s
Speed in water = 2.25×10⁸ m/s