Encore - Triple Rainbows

July 28, 2018


Today and every Saturday Earth Science Picture of the Day invites you to rediscover favorites from the past. Saturday posts feature an EPOD that was chosen by viewers like you in our monthly Viewers' Choice polls. Join us as we look back at these intriguing and captivating images.

Photographer: Dara Korra'ti
Summary Authors: Dara Korra'ti; Jim Foster

January 2013 Viewer's Choice It’s a treat to see a rainbow painting the sky, and seeing a double rainbow always gets our attention, but how many of us have seen three bows at the same time? The rainbow trips shown above were photographed near Kenmore, Washington (northeast of Seattle) in the late afternoon on November 24, 2012. Sandwiched between the two arching bows is the third bow – bent at a vertical angle. The bright primary bow (leftmost) and fainter secondary bow (rightmost) are a result of refraction and reflection of sunlight in raindrops – a second reflection within the drops creates the secondary bow. However, the odd bow isn’t due to a third raindrop reflection but rather to reflection off nearby Lake Washington, southwest of the photographer’s location. Sunlight reflecting off the smooth water of the lake interacts with the falling raindrops to form the reflection rainbow. Note that its color scheme is the same as that for the primary bow – blue on the inside and red on the outside. You have a better chance to observe a reflection bow when the Sun is low in the sky because sunlight is not reflected as readily from a high Sun.

There also seems to be a very, very faint, nearly vertical structure where you would expect the secondary reflection bow to appear -- at upper right, more or less pointing toward the tallest conifer. It's hard to say just what it is since it's at the limit of visual perception -- it could just be part of the structure of the cloud.

Photo Details: Camera Maker: Canon; Camera Model: Canon PowerShot G9; Lens: 7.4-44.4 mm; Focal Length: 7.4mm; Aperture: f/4.0; Exposure Time: 0.0016 s (1/640); ISO equiv: 200; Exposure Bias: -0.33 EV; Software: QuickTime 7.6.6.