Iridescence Above Bedford, Ohio
August 19, 2010
These shimmering altocumulus clouds appeared above an approaching storm near Bedford, Ohio, late in the day on July 23, 2010. Iridescence nearly always occurs in mid-level altostratus or altocumulus clouds (between 5,000 ft and 15,000 ft or 1,524 - 4,572 m in altitude). Such clouds are made up of tiny water droplets which, because of their minute size, deflect sunlight rather than refract or reflect it. When a wave, in this case waves of light, encounters an obstacle such as a small droplet of water it's bent and spread out in such a way to produce overlapping colors -- the process of diffraction. The brightest and purest colors result when the droplets are of the same size throughout the cloud.
Photo details: Camera Maker: Canon; Camera Model: Canon PowerShot SX120 IS; Focal Length: 28.1mm; Aperture: f/4.0; Exposure Time: 0.0010 s (1/1000); ISO equiv: 80; Exposure Bias: none; Metering Mode: Matrix; White Balance: Auto; Flash Fired: No; Orientation: Rotate 90; Color Space: sRGB