Rhodopsin is the light absorbing pigment found within rods and is responsible for the initial absorption of light. Rhodopsin is made up of vitamin A and a protein called opsin.
the primary function of Rhodopsin is to convert light absorbed within the eye into an electrochemical signal and send it to the brain for interpreting. It is more active when there is less light present and is most sensitive to blue-green light.

Figure 11.1 represents the absorption of Rhodopsin along the electromagnetic spectrum of visible light.

Aubusson, Eileen Kennedy Peter. Biology in Context: the Spectrum of Life. Victoria : Oxford Uni. Press., 2001. Print.
"HSC Online." NSW HSC Online. N.p., n.d. Web. 25 June 2010. <http://www.hsc.csu.edu.au/biology/options/communication/2952/CommPart4.html#1>.