What describes the refractive index of a material's effect on light bending?

The refractive index of a material is a measure of how much light slows down and bends when it enters that material from another medium, such as air or vacuum. This characteristic is closely associated with optical density, which refers to the amount of light that a material can absorb or transmit. A higher refractive index indicates that light travels more slowly in the material and bends more sharply as it passes from one medium to another.

When light encounters a boundary between two different media, its speed changes, leading to a change in direction or bending of the light rays, which is effectively described by the refractive index. Thus, optical density serves as an essential factor in determining how significantly light will bend when entering a new medium, making it the correct answer in this context.

The other options relate to aspects of light behavior, but they do not specifically capture the relationship between the refractive index and the bending of light. Curvature refers to the shape of a lens or surface, light dispersion refers to the separation of light into its component colors, and the refraction angle is the angle at which light bends but does not directly define the effect of refractive index.