Which type of light behavior is influenced by the refractive index of a medium?

The behavior of light that is influenced by the refractive index of a medium is the refraction of light. Refraction occurs when light passes from one medium into another, and changes its speed as a result of the differing refractive indices of the two materials. The refractive index is a measure of how much light slows down in a medium compared to its speed in a vacuum.

When light enters a new medium at an angle, its speed changes, causing it to change direction. This bending of light is described by Snell's Law, which relates the angle of incidence and the angle of refraction to the refractive indices of the two mediums. Thus, the degree of bending is directly influenced by the refractive index.

The other behaviors listed do not fundamentally rely on the refractive index. While absorption refers to the way materials absorb light energy, and diffraction involves the bending of light around obstacles and through openings, neither of these phenomena is directly controlled by the refractive index. Furthermore, transmission of sound is unrelated to the optical properties of light, as it pertains to a different wave phenomenon altogether.