The addition of barium also increases the refractive index. Thorium oxide presents glass a superior refractive index and small dispersion and was previously used in producing higher-high-quality lenses, but because of its radioactivity has been changed by lanthanum oxide in modern eyeglasses.[eighty four] Iron is usually incorporated into glass to https://commercial09753.wikikali.com/819406/an_unbiased_view_of_door