Iridescence in a Dandelion Seed Head

May 08, 2011

Photographer: Nikolas Wall 
Summary Author: Nikolas Wall; Jim Foster

May 2011 Earth Science Picture of the Day Viewer's Choice

The photo above showing iridescence in a dandelion (Taraxacum officinale) was captured in a field near Hillsborough, North Carolina. Diffraction of sunlight by the dandelion's seed head is responsible for the pastel coloration. Each head is composed of hundreds of fine rays, which are just the right diameter (several micrometers) to deflect light -- the ray filaments interfere with wavelengths of visible light. Minute variations in the thickness of the rays deflect light differently, resulting in differences in color and brightness intensity. Photo taken on April 14, 2011.

Photo details: Camera Maker: NIKON CORPORATION; Camera Model: NIKON D3100; Focal Length: 52.0mm (35mm equivalent: 78mm); Aperture: f/16.0; Exposure Time: 0.0010 s (1/1000); ISO equiv: 100; Exposure Bias: -1.33 EV; Metering Mode: Matrix; Exposure: program (Auto); White Balance: Auto; Flash Fired: No; Color Space: sRGB.