Which type of glass has a high refractive index of 1.65 and contains lead?

Flint glass is characterized by its high refractive index, which can reach around 1.65 or higher, primarily due to its lead content. The incorporation of lead oxide into the glass formulation increases both the refractive index and the dispersion of the glass, making it particularly suitable for optical applications and fine glassware. This unique property allows flint glass to bend light more effectively, enhancing the clarity and brilliance of optics like lenses and prisms.

In contrast, crown glass typically has a lower refractive index, usually around 1.50 to 1.55, and does not contain lead, making it less suitable for applications requiring a high refractive index. Optical glass refers more broadly to any type of glass used for optics and can have various compositions, but it doesn't specifically refer to leaded glass. Crystal glass, while often high in lead content, is typically designed for decorative rather than optical use, and its refractive index may vary but is generally defined within the context of its use in fine glassware. Thus, flint glass is the optimal choice for its specific properties tied to lead content and its high refractive index.