Physics Photo of the Week
April 20, 2012
Almost two years ago (May 16, 2010) I
had a chance to capture a rainbow happening with a time
lapse. The rain had passed so I didn't have to worry
about getting the camera wet. This was a typical
afternoon rain shower typical of the season in the
mid-afternoon. By studying the animation, we can see the
distant rain squall passing along the Swannanoa Valley and
more rain appearing in the sunlight and creating the familiar
rainbow. Notice not only is the rain squall traveling to
the left and lengthening the bow, but the rainbow is also
slowly rising in the sky reflecting the passage of the Sun
lower in the sky as time progresses. The Sun is behind
the camera (always for a rainbow). With the Sun becoming
lower in the sky the rainbow is rising in the opposite
direction - keeping the same constant angle between the Sun's
direction and the arc of the rainbow. The physics of the
rainbow is explained in other PPOW's: Oct.
29, 2010 and April
4, 2008;
A related droplet phenomenon is shown in a Spider's
rainbow.
At right is a full-frame photograph of this
rainbow showing the storm clouds that produced the spotty
rain.
Physics Photo of the Week is published weekly during the academic year on Fridays by the Warren Wilson College Physics Department. These photos feature interesting phenomena in the world around us. Students, faculty, and others are invited to submit digital (or film) photographs for publication and explanation. Atmospheric phenomena are especially welcome. Please send any photos to dcollins@warren-wilson.edu.
All photos and discussions are copyright by Donald Collins or by the person credited for the photo and/or discussion. These photos and discussions may be used for private individual use or educational use. Any commercial use without written permission of the photoprovider is forbidden.
Click here to see the Physics Photo of the Week Archive.
