Photon Posted on 13th December 201513th May 2021 by ThePD (The Project Definition) A Photon is a particle of light or other electromagnetic radiation that acts as an individual unit of energy. Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window)Click to share on LinkedIn (Opens in new window) Related Posted in Science and tagged physics. ThePD (The Project Definition) ThePD has been developing the Preferred Project Definitions based on the actual project execution and operation experiences and knowledge with the Project Language, and sharing with you daily basis.