1. The ligand field causes the splitting of d orbitals of the central metal atom into two sets (t2g and eg).
2. When the white light falls on the complex ion, the central metal ion absorbs visible light corresponding to the crystal field splitting energy and transmits rest of the light which is responsible for the colour of the complex.
3. This absorption causes excitation of d – electrons of the central metal ion from the lower energy t2g level to the higher energy eg level which is known as d – d transition
