AExplain How the Crystal Field Theory Can Use the Magnitude $\Delta$

Essay

a.Explain how the crystal field theory can use the magnitude of the splitting energy $\Delta$ to provide an explanation of the color and magnetic properties of octahedral complexes.
b.In promoting an electron from the t_2g set of orbitals to the e_g set,an octahedral complex absorbs a photon with a wavelength $\lambda$ of 523 nm.Calculate the value of $\Delta$ in the complex,in kJ/mol.