The light's path or light's path? Can I use articles with apostrophes?

I've been told that "The Dirac's equation" is not grammatically acceptable. The correct should be "Dirac's equation" or "The Dirac equation".

I'm wondering if this has something to do with Dirac being the name of someone or if this is a general rule. My case, specifically, concerns the phrase I used in the title. Which one is the correct version:

a - "(...) the correction of the light's path"

b - "(...) the correction of light's path"

c - "(...) the correction of the light path"

What I mean is the path that a ray of light follows.

Thank you very much.