Chemistry - Coordination Chemistry Question with Solution | TestHub

Both ruby and emerald owe their colour to ${\mathrm{Cr}}^{3+}$ in an octahedral oxide environment. In emerald the host lattice (beryl) produces a weaker crystal field than in ruby (alumina), so the absorption bands shift to longer wavelengths - emerald absorbs in the yellow-red and blue regions.

The light left over and transmitted is therefore in the green region, which is why emerald appears green. Answer: (C)