Electronic Spectroscopy is concerned with the excitation of electrons with visible or ultraviolet light to atomic or molecular orbitals. Energy gaps exists and of which values are determined of E=hν where E is energy, h is Planck's constant, and ν frequency equal to c/λ with c in the speed of light and λ a wavelength. Wave-particle duality is shown through h/λ=mc. Hamiltonians, Born-oppenheimer approximation, Jablonski diagrams all help to illustrate electrons in orbit. A spectrometer measures light as it is passed through matter, a transparent medium, and the promotion of an electron in it's ground state to an excited state. It deals with a white light excitation source, sample, and detector.