Aparticular material has an index of refraction of 1.25. what percent of the speed of light in a vacuum is the speed of light in the material?

The percentage of speed of light in vacuum to the speed of light in the said material is 80%

Explanation:

The common values of refractive index are between 1 and 2 since nothing can travel faster than the speed of light, therefore, no material has a refractive index lower than 1.

According to the formula

where is the index of refraction

is the speed of light in vacuum

and is the speed of light in the material, it can be seen that n and v are inversely proportional which means greater the refractive index lower is the speed  of light.

Since we know that speed of light in vacuum is 300,000 km/s using the formula we get,

for finding percentage,

%