The correct option is (b) deep-blue.
Explanation:
Glass is an amorphous and transparent or translucent solid obtained by solidilication of a mixture of silicates of different metals. one of which is always arr alkali metal. Addition of small amounts of transition metal salts to the glass mixture imparts colour to the glass. For example, addition of small amounts of Fe3+ Fe2+, Co2+, Cr3+ and Mn4+ salts imparts yellow-brown, light blue, deep blue, green or violet colour respectively.
