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Old 18-05-2011, 05:38 PM
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renormalised (Carl)
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Originally Posted by Keshdogga View Post
Yes guys thanks for the responces =] But I'm still curious as to what the interaction is between light and the particles of the medium that causes it to bend at a predictable angle.

So we can obviously agree that the medium does not effect the speed of the light, light still always travels at c, it's only its apparent decrease in velocity. But when i try to imagine why the photon bends like a car turns one direction when it hits water i hit a dead end. the car does this because one side is going slower than the other not because the whole car has slowed and turned. Maybe this isn't an accurate example or i'm interpreting it wrong??

This is my unfulfilled understanding with the gaps

So the photon (singular) interacts with the molecules (i still don't know how (absorbed by electrons and re-emitted giving the appearence of 'bouncing' from atom to atom??)) in such a way that it appears to bend predictably. Should the light not just scatter if this is true?
The light doesn't act as a particle, it acts as a wave. The velocity of the light does, in reality, decrease as it enters the denser medium. It's not an apparent decrease. The direction of travel changes because the wave changes its velocity upon entering the denser medium. Those parts of the wave still outside the medium remain at their original velocity until they enter the medium. You answered your question in the bold analogy, above. You have to get used to thinking along the lines of the particle-wave duality. A photon is both simultaneously and it's acting as a wave when it enters the interface between the two media.

Light also scatters and does act as particles as well

You have two types of scattering/reflection, Specular and Lambertian. Specular scattering/reflection occurs when light strikes a surface and then scatters (reflects) back at the same angle it strikes that surface, much like a mirror. Lambertian scattering (reflection) is where the incident light strikes a surface and scatters equally in all directions, no matter the angle of incidence. Calm water is a specular scattering surface and the reason why it acts like a mirror when you look into it. An example of a Lambertian scattering surface would be sandpaper....basically any rough textured surface will scatter light in all directions, no matter the incident angle of the incoming rays (this being within reason...a mountain range is not a Lambertian reflection surface!!!).
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