light

[groovy chick]

How does light shine off on silver in bright sunlight

[jake-the-peg]

I'm glad you guys find this so easy maybe you can explain it to me.

Let's see white paper reflects all the light that hits it but it doesn't look like a metal sheet.

I think it might be to do with all the free electrons in a metal but I can't quite remember maybe you can help me out?

[Dacetine]

Richard Feynmann describes how reflection works in his great (and, incredibly, quite readable) book on Quantum Electrodynamics (QED). Believe me, if it is true then everything they tell you in school is way off the mark. It goes something like "photons of light are reflected off the surface of the metal and take all possible paths to your eye (all "histories")". You would think this would lead to a complete mess, but fortunately "all the paths cancel out except the one that corresponds to the shortest (i.e. straight-line) distance" and, hey-presto, a reflection.

I think white paper absorbs the photons of sunlight and then reradiates them. Therefore this is reradiation but not reflection.

[jake-the-peg]

Yeah, it's far from trivial. My understanding is that light incident on a point is absorbed by a white material and reradiated at all possible angles. This light does not cancel out because when you move your eye you still see it.

This is why you get glow in the dark bras at discos - white materials also tend to absorb UV and reradiate at lower frequencies (flourescence). White materials haveing a large number of different frequencies that they can absorb and re-radiate. 

The cancelling out bit comes in the construction of a hologram where no lens is used consequently all points of the film get all parts of the image and the image is reconstructed when the laser light illuminates it again as it interferes canceling out at certain points to give an image.

I think the point about reflection from a metal is that the "sea" of free electrons can absorb and reradiate any photon and is not just limited to a number of quantum states so the re-radiated photon has *exactly* the same frequency as the incident one. 

[Tim Baxter]

Keep it simple!

Mirrors are 'silvered' behind the glass to reflect light.  The silvering is nowadays made from aluminium 'melted onto the glass.  In olden days (before a glimpse of stocking was looked on as something shocking) 'burnished' (highly polished metal and smooth like glass) was used as a reflector for ones personal vanity.  So any smooth surface will give a more coherent reflected image as apposed to a rougher surface which will reflect light in all directions and give a less defined image.