Which lens type has an index of refraction of 1.498?

The lens type with an index of refraction of 1.498 is CR-39 lens. This specific refractive index is characteristic of CR-39, which is a commonly used plastic lens material known for its lightweight and impact-resistant properties. It is often preferred in eyewear due to its favorable combination of optical clarity and reduced weight compared to glass lenses.

Crown glass lenses typically have a refractive index around 1.52, making them denser and heavier than CR-39. Polycarbonate lenses have a lower refractive index of approximately 1.586 and are also known for their strength and resistance to impact. High index lenses, designed to be thinner and lighter than standard lenses, usually start from around 1.60 and can go up to 1.74 or higher.

Thus, CR-39 is specifically identified by an index of refraction close to 1.498, making it the correct answer in this scenario.