My friend recently bought a high-powerd pocket laser pen (from China). It is green, and reflects off most surfaces as green.
On some orange surfaces, it reflects orange instead. That is to say, we see an orange dot instead of a green one.
It seems to be certain hard, shiny plastics (for example a Kryptonite bike lock). Orange fruit peel, for example, reflects green, and most orange fabrics reflect green.
I suspect it's some kind of pigment that is reflecting this way.
When the reflection is orange, the intensity of the reflection is subjectively about the same, i.e. it doesn't seem to be losing much energy. If one shined light from a green incandescent bulb onto an orange surface, one would expect that surface to be lit less intensely than a white surface. Not so the laser.
So it seems to be that the photons are being re-emitted at a different wavelength than they were absorbed at.
How can this happen? And why is it only orange?