At 7/18/09 05:00 PM, Toast wrote: I have a question that's been eating my mind. When you shine a light on a window, part of the light will be reflected back to you, which shows a faint reflection of the inside on the glass, and part of the light continues outside through the window which is why someone standing outside the house can see what's happening inside through the windows. Now that's easily understandable if you think of light as waves, but the strangest thing is that it's made of particles (photons), and that some of them are reflected not when they reach the end of the window, but on immidiate contact with the window glass. How does each individual photon know whether to be reflected or not? And if it is reflected, how does he know to reflect on contact with the mirror as if it already knows the thickness of the window? (thicker windows means more photons are reflected)
I'm afraid this has nothing to do with quantum physics, and is actually just a matter of the critical angle between air and glass - the angle at which light no longer is refracted, but starts getting reflected.
I'm pretty sure, the reason why some light is refracted, and some is reflected is purely because glass isn't smooth. It looks at feels smooth, but if you go down to a microscopic level, the surface will appear quite rough. When light reaches the glass, most of it is at an angle less than the critical angle and so just goes straight through. However, some of the light hits the glass at a larger angle (due to the small imperfections in the glass) and so instead of being refracted, it is reflected back to you so you see your reflection.
The light has two different places it could be reflected - entering the glass, and exiting it.
As for why more photons are reflected by thicker windows, i can't say i have ever noticed this happening. I can't see any reason why it would happen. Could you give an example of when you might see this happening?
