I made this comment yesterday in another thread, but it provides some of 'why' for the colors we see in stained glass.<p>> You've seen it before... Stained glass. Stained glass was one of the first use of nanoparticles and plasmonics to become commonplace. The wide range of colors that you can get in stained glass is due to the nano properties of the materials you add to the glass. The effect is due to surface plasmons - electric field waves that travel on the surface of conductors. Much like ocean waves, plasmons are created from light's electric field. They bounce back and forth, and since they are only permitted on the surface of a material, there are limits on what waves can exist. This is what gives them the weird properties - the size and shape determine the optical properties.<p>On another tangent (this one's pretty cool) - since you can tune the properties of these nanoparticles, you can make them respond in a specific way. Let's say we have a cancer cell that we want to kill, and only that cancer cell should die. We can create nanoparticles that bond with that cancer cell, and only that cancer cell. But how do we kill it? We can tune the absorption spectrum of the nanoparticle to absorb infrared light - light that is transparent to the human body. We create a small heater that absorbs tons of the input energy, while keeping the rest of the area cool. Localized heating destroys the nearby cancer cell.<p>Plasmonics are really cool - <a href="http://en.wikipedia.org/wiki/Plasmon" rel="nofollow">http://en.wikipedia.org/wiki/Plasmon</a>
<a href="http://en.wikipedia.org/wiki/Plasmonic_Nanoparticles" rel="nofollow">http://en.wikipedia.org/wiki/Plasmonic_Nanoparticles</a>