The formula n = c / v can be used to determine the index of refraction (n) of a material from the speed of light (v) in that material (1.25).
Speed of light in air is c. Let the refractive index of medium with respect to air is n.
Speed of light in medium decreases by 40% of c.
Thus speed of light in medium v= 0.8c
using n=c/v
⟹n=c/0.8c
⟹n=10/8=1.25
The refractive index of a material (n) is determined by dividing its light-moving velocity by the speed of light (c) (v). We may see the link about v by rearranging the equation. The speed of light increases with decreasing refractive index.
The refractive index of the vacuum is 1. The equation can be used to determine the refractive index of different materials. The optical density increases with the refractive index, slowing down the speed of light.
Learn more about refraction here:
https://brainly.com/question/14760207
#SPJ4