The refractive index of a material is a dimensionless number that describes how fast light travels through the material. It is defined as n={\frac {c}{v}}, where c is the speed of light in vacuum and v is the phase velocity of light in the medium.
the ratio of the velocity of light in a vacuum to its velocity in a specified medium.
The best answer is that it reduces the level of ground water
I say that the answere would be B
The answer is C. An occluded front.
Answer:
velocity = frequency * wavelength
Given the wavelength one must also have the frequency.