Water Drops, Daisies and Bumblebees
May 14, 2012
Photographer: Mila Zinkova
Summary Author: Mila Zinkova; Andy Young; Jim Foster
The photo above provides a wonderful demonstration of the physics of light in water drops as well as the attraction of water molecules to plant molecules and to one another. In this case, the liquid drops result from rain and fog. A drop of liquid behaves like a simple lens – just like a camera. Therefore, the refracted image is upside-down when viewed through the drop. Somehow, bees, such as this bumblebee, figure out this hall of mirrors and are able to get to the daisies’ nectar.
Note the different contact angles of the drops on the plants’ surfaces. In some places the plant cuticle is waxy and the contact angle is close to 90 degrees (the molecules of the drop are only weakly attracted to the molecules of the plant surface); in other places where the water wets the surface, for example, the contact angle is closer to zero degrees. Wettability plays an important role in the bonding of two materials and is responsible for capillary effects. Photo taken early last summer in San Francisco, California. [Revised November 2017]