According to the standard model (afaik) light exists as a wave-particle duality. Sometimes it's a wave, sometimes it's a particle. To get light to travel through a vacuum and eliminate aether, the particle theory became widely accepted. Light isn't matter, even as a particle (photon) because it carries energy and momentum, but has no mass. Being able to pass through glass is *sorta* tricky, because not all light passes through glass. The visible spectrum does, yes, but ultraviolet light doesn't. Gamma rays are absorbed by mostly everything that exists. So even though something's transparent, that doesn't mean all light passes through it, just some. Like x-rays passing through flesh but not bone. It's the source of the heat that makes the light. For deflection or reflection, it is easier to think of light as a wave. Any wave passing though a medium under certain conditions will deflect or reflect. I think that about does it. For more information I would suggest http://www.howstuffworks.com and http://www.particleadventure.org (not completely sure if the second link is correct). -paperclip