Why does a cut diamond sparkle?

A cut diamond sparkles due to total internal reflection, which corresponds to option [C]. The geometric arrangement of a diamond’s facets, combined with its high refractive index, allows light entering the diamond to bounce internally from facet to facet rather than escaping. This phenomenon, known as total internal reflection, ensures that a significant portion of light remains trapped within the diamond, enhancing its brilliance and dispersion of colors. The precise cutting of diamonds into facets optimizes this effect, scattering light into a spectrum of colors called “fire.” This inherent property of diamonds, stemming from their crystalline structure and high refractive index, distinguishes them as prized gemstones renowned for their exceptional sparkle and optical allure. Understanding the physics of light interaction within diamonds is crucial for gemologists and jewelers in evaluating and appreciating their beauty and value.