Answer: c. Refraction
Refraction is a phenomenon in which a light wave bends or changes its direction when passing through a medium with a refractive index different from the other medium.
Being the refractive index
is a number that describes how fast light propagates through a medium or material, and is defined as the relation between the speed of light in vacuum (
) and the speed of light
in the second medium:
It is important to note that in this process, the wavelength may be modified because it depends on the medium, however, the refracted ray of light does not change its frequency.