I am curious about the transparency of some materials to visible light. My physics is patchy and self taught, so I am hoping you can fill in a gap for me, or correct a misconception. So, transparency comes about when the light in question passes through a material with electrons that cannot accept the photons energy to jump to a different energy band (or get bumped from their atoms -photovoltaic effect?) In opaque materials then, there must be a compatability between energy availble from photon and energy gap for the materials electrons. Even if this is not right, I am at peace with this explanation! However, I thought the photon has no electric charge, and is very small. I have read that neutrinos speed through us without reaction constantly, and the properties for attaction to other particles of a photon do not sound too different, so why do they not just pass through unaffected too? How come so many of them manage to hit an electron? What is the attraction force I am not aware of?