What is the approximate index of refraction and abbe value for Polycarbonate (plastic)?

• A. n=1.523, abbe=58.9
• B. n=1.498, abbe=58
• C. n=1.586, abbe=30
• D. n=1.53, abbe=44

Answer: (C)

Polycarbonate is a plastic with a relatively high index of refraction and moderate dispersion. The index around 1.58 means light bends quite a bit as it enters the material, which is why polycarbonate lenses can be thinner yet still strong. The Abbe number, a measure of how much the refractive index changes with wavelength (lower Abbe means more chromatic dispersion), is about 30 for polycarbonate. This combination—n ≈ 1.586 and Abbe ≈ 30—fits what we know about polycarbonate: strong bending but noticeable dispersion. The other values either give a lower index with higher dispersion or a higher dispersion value that isn’t typical for this plastic, so they don’t match polycarbonate as closely.