refractive index

[L33NA]

hey all

for an assignment at uni i need to write up about refractive index...any ideas on why it is important in optics??--other than makes lenses thinner?

thanks
leena

[HarryChiling]

no longer playing in this sand box

[Darryl Meister]

The refractive index has several applications and implications in spectacle lenses:

• As the refractive index of a lens material increases, the lens becomes thinner and lighter in weight since the curves are shallower.
• As the refractive index of a lens material increases, the Abbe value generally decreases, resulting in an increase in dispersion and a reduction in optical performance.
• If the refractive index is above 1.530, the material is considered a "high-index" material.
• As the refractive index of a lens material increases, the surface reflectance of the lens material also increases.
• The refractive index of a lens material varies across the entire visible spectrum, becoming highest in the blue end and lowest in the red end.
• The refractive index is important in lens surfacing for determining the effective power and precision of lap tools.
• The are two "reference index" values in use internationally, the Helium d line and the Mercury e line, and the measured focal value of a lens will depend upon the reference index.
• If there is a difference in refractive index between the scratch coating and the lens material, interference fringes may result.
• Layers of alternating refractive index are used to eliminate reflections in antireflection coatings.