How does light "illuminate" objects? (help me in a debate) Hello, I'm curious as to how light illuminates an object. To be more specific how does light allow give an outline to a body? Can an seemingly physical object be visible to the naked eye and at the same time be non-physical? I know this seems like a nonsensical question, but I'm having a debate with a person and need 'backup' so to speak. I'm trying to make the claim that if a non-physical entity is visible, then the object can not be non-physical, because the wavelength of the light would not be interrupted. If anyone can provide a link or source I would appreciate it greatly. I know that the wavelength of the light an object is viewed under is somehow a limiting factor in resolution. However, I'm not sure if this relates to my question or not. P.S. I may have made spelling mistakes, but I'm in a rush, so please forgive me.