The reflection is a mirage, a virtual image. Where is the second beam of reflection?
There are more than two beams. The under surface of the bottle is curved, parabolic. The 'vortex' disappears when, with both hands, one surrounds the bottle cap with the index fingers and thumbs.
We shall call this phenomenon，'小漩涡借路'.
Does a droplet and a vortex share the same surface profile with one inverted but opened?
