2. Ruby is the mineral corundum with small amounts of Cr+ substituted for A1+. The 3d electron in Cr+ can be excited to levels that are 2.2 eV and 3.0 eV higher in energy. a) Determine the wavelength of the photons that are absorbed by transitions to these states. b) In what portion of the visible spectrum do these wavelengths lie? c) Based on your findings, discuss the origin of the color of ruby.