Which phenomenon is directly influenced by the refractive index of a material?

The speed of light within a material is directly influenced by the refractive index of that material. The refractive index is defined as the ratio of the speed of light in a vacuum to the speed of light in the material. A higher refractive index indicates that light travels more slowly in the material compared to a vacuum. This relationship means that when light enters a medium with a different refractive index, its speed changes accordingly.

For example, when light moves from air (with a refractive index close to 1) into glass (which has a higher refractive index), its speed decreases, leading to phenomena such as bending and refraction at the interface of the two media. This principle is fundamental in optics, impacting how lenses are designed and how various optical systems operate.

The other options, while they relate to different physical properties, do not have a direct connection to the refractive index in the same way. The energy consumption of a material pertains to its electrical properties and how it interacts with energy, elasticity refers to mechanical properties, and magnetism is associated with how materials respond to magnetic fields. None of these properties are specifically governed by refractive index.