Which one of the following types of glasses is used for making optical instruments?

Flint glass is specifically designed for use in optical instruments due to its high refractive index and high light-dispersing power [1]. It is a lead-based or potassium-based glass that is significantly denser than ordinary glass, making it ideal for the production of high-quality lenses, prisms, and binoculars [1]. While other types of glass like Pyrex (borosilicate) are valued for thermal shock resistance in cookware and labware, they are not the primary choice for precision optical systems. Optical glass is categorized into two main types: crown glass and flint glass. Flint glass, with a refractive index typically ranging from 1.45 to 2.00, is essential for correcting chromatic aberrations in optical systems when combined with crown glass [1]. Its unique chemical composition, often including lead oxide, allows it to manipulate light accurately for analytical, medical, and photographic equipment.

Sources

1. [1] https://www.sciencedirect.com/topics/materials-science/borosilicate-glass