Reflecting coke cans

[Paul King]

About the Coke can  (great picture ) ­ there is a chance that the logo paint
used is reflective paint ­ that is retro-reflective ­ the incident light is
reflected back along the incident path. Meaning that there will be no light
(or hardly any) reflected at angle of incidence = angle of reflection. This
is achieved in the paint by having it full of (tiny) transparent spheres ­
light incident from any direction basically does several total internal
reflections and emerges going  back the way it came in. Its the stuff used
in road signs (so your  headlights shine back at you ) and stick on
reflective tape.
Why would you use it on Coke cans?

If this is the real reason then the ³white² reflection from the black
edgeing is in fact just a ³bright² reflection from something that is shiny (
a specular reflection); no matter that it is a dark  colour.

Just thought. Bright Sunlight on road signs can give off a rainbow
reflection. I had assumed that this was some sort of thin film interference
effect but now wonder if it might be an actual "rainbow" with the colour
separation bought about by change in velocity instead of change of phase.
Its a bright morning here on the Coast - I'm goig  down the road to have a
look at the Stop signs.

Paul King