Optical Glass — Choice for Lenses and Prisms Which type of glass is characteristically used for making optical lenses and prisms because of its relatively high refractive index and dispersion?

Introduction / Context:
Basic optics items test your familiarity with glass types. Optical elements often exploit materials with specific refractive indices and dispersions. Historically, pairs of crown and flint glasses are combined to correct chromatic aberration. Knowing which glass has higher dispersion is crucial to answer questions on prisms and lenses.

Given Data / Assumptions:

• Objective: identify glass suitable for lenses/prisms due to optical properties.
• Key properties: refractive index and dispersion (Abbe number).
• Candidate types: flint, crown, pyrex, etc.

Concept / Approach:

Flint glass (traditionally lead-rich) exhibits a higher refractive index and greater dispersion than crown glass, making it excellent for prisms and as the high-dispersion element in achromatic doublets. Pyrex (borosilicate) excels in thermal shock resistance, not high dispersion. “Soft glass” is a vague category; “jena glass” is a trade/type reference but not the standard answer in foundational exams. Hence, flint glass is the correct choice.

Step-by-Step Solution:

Recall: crown (low dispersion) + flint (high dispersion) pairing in optics.Prisms benefit from higher dispersion to separate colors → flint glass.Discard pyrex (thermal duty) and generic/brand-like terms.Select “flint glass.”

Verification / Alternative check:

Achromat design uses crown–flint combinations; prisms for spectroscopy often specify flint types to maximize angular dispersion.

Why Other Options Are Wrong:

pyrex: Low thermal expansion, not selected for dispersion.soft glass / jena glass / crown glass: Do not match the “high dispersion” requirement as directly as flint.

Common Pitfalls:

Picking pyrex because it sounds technical; the property relevant here is optical dispersion, not heat resistance.

Final Answer:

flint glass