• (n.) The doctrine or science of light, explaining its nature and phenomena; optics.
Pho·tol'o·gy noun [ Photo- + -logy : confer French photologie .] The doctrine or science of light, explaining its nature and phenomena; optics. 
photology 1. A branch of physics that deals with light or the study of light and its effects. 2. That science concerned with the production of light and energy; especially, regarding therapeutic applications.