Marine biologist
scientist
If you are meaning the light spectrum, Physicists study all forms of light and waves and what they do.
A biologist studies all life forms, including animals, plants, and microorganisms. They focus on understanding the structure, function, behavior, and evolution of living organisms.
oceanographers DarkFoxy: and marine biologists or is that the same thing.... well either way its another term
A mineralogist studies minerals.
An ecologist studies pollution
The kind of scientist who studies Urology would be a Biologist, since Urology concerns a biological function (urination). If you mean the kind of doctor who studies Urology, that would be a Urologist.
meteoroligists
Audiologist
An Ichthyologist.
Botanist
cosmologists