How does refraction of light work

[peter.ell]

I've looked into refraction of light, and I understand the basic principles thoroughly, but there are a few things that I don't understand, if you know any of the answers to these questions, please help me:

1.) Why does light bend when it slows down instead of just continuing on in the same direction after being absorbed, held, and then emitted by the electrons in the medium? Why don't the electrons emit the light in the same direction after they absorb it? And how does simply increasing the delay between absorption of light and emission of light cause it to bend more? This doesn't make much sense.

2.) Why are different wavelengths of light refracted to different degrees? I know it's because different wavelengths are slowed to different degrees, but what causes this? Aren't different wavelengths absorbed or transmitted depending on how the electrons in a specific material interact with each wavelength of light, yet all transparent materials slow blue light more than red light, why? What causes does one wavelength travel slower than another?

3.) How is it possible for the colors of a rainbow to be so pure? Given what I learned about the light paths for different colors in a rainbow, I know that red light is not only refracted at the angle where red is seen in a rainbow, but also at all the other angles. Given this, it means that, while green light is not refracted at the top of a rainbow where red is, red happens to be refracted where green is... which should mean that we would not be able to see any of the colors in a rainbow except for red and whatever the combination of red and all the other colors turns out to be. Yet we don't, why not?

My utmost thanks for helping me understand these questions!

 

[kanato]

1) The light is re-emitted in the same direction. Notice how once the light is in the medium, it travels in a straight line. The bending of the light when entering a medium is a *surface* phenomenon. See the animation here: http://en.wikipedia.org/wiki/Snell's_law#Derivations_and_formulae . Notice how the wavefront travels horizontally across the surface at a faster rate than it travels within the medium. This causes the change in direction of the wavefront in the medium.

2) From a quantum mechanical perspective, the reason light is slowed when traveling through a medium is it interacts with virtual states. Virtual states aren't "real" states in the sense that you can't promote an electron to that level and leave it there (using sloppy language here). Virtual states exist within the band gap of the material. IIRC, the lifetime of a virtual state depends on how close it is in energy to a real state. Virtual states of a higher energy are closer to the conduction band in the material, so they have a longer lifetime. Because of this longer lifetime, it allows for the light to be absorbed for a longer period of time, resulting in a larger delay before it continues merrily on its path. Since blue photons have higher energy, they are slowed down more than red photons.

3) I'm not very clear on your question. The refraction at every angle just means you can see the rainbow no matter where you stand.