Question

formula of light speed​

Answer 1

In a vacuum, it is a constant (c) equal to 3.0 × 10^8 m/s. However, light moves slower in non-vacuums, such as through glass or air.

In that case, v=c/n, where v is the new speed through the material, c is the speed of light in a vacuum, and n is the refractive index.