Which factors affect the speed of light in a medium?

The speed of light in a medium is fundamentally determined by how that medium interacts with light, which is closely related to both its density and refractive index.

The density of a medium influences how closely packed the molecules are, affecting how light waves propagate through it. A denser medium typically slows down light because the light waves interact more frequently with the molecules within the medium.

The refractive index quantifies this effect, indicating how much light is bent, or refracted, as it enters a new medium. A higher refractive index means that light will travel more slowly in that material compared to a vacuum.

Both of these factors — density and refractive index — are essential in describing how the speed of light is modified when transitioning from one medium to another, making this choice the correct answer.

In contrast, the color of the light and distance traveled do not inherently change the speed of light in a medium; rather, the speed can vary based on the medium’s properties. The angle of incidence and surface texture affect how light interacts at the boundary between different media but do not directly affect the speed of light within a specific medium. Lastly, the presence of electronic devices does not influence the speed of light in a medium.