Why is the human visual system sensitive only to light of wavelengths from approximately 760 to 380 nm?: An answer from thermochemistry and chemical kinetics Original Research Article

The range of visible light has been explained by the knowledge available of gas-phase thermochemistry and chemical kinetics. The C, C–π bond dissociation energy at the 11 and 12 positions of the rhodopsin complex is estimated to be approximately 37.4±1.5 kcal/mol. This energy is just equivalent to wavelength of the red limit of the visible light. The photons of the violet limit (approx. 75.2 kcal/mol) can break the weakest C–C and H–C bonds in important species involved in the photo-induced cis–trans isomerization cycle and can stop the visual cycle.