Physics Photo of the Week

Physics Photo of the Week November 17, 2023 Brilliant Rainbow - Photos and diagrams by Donald F. Collins This brilliant rainbow was seen several weeks ago (October 20, 2023).  The rain that day (0.10 inch) was the final rain before the onset of a severe drought - not relieved until a light rainfall over three weeks later (0.21 inch) on November 11. Rainbows appear only when both rain and sunlight are present at the same time.  The rain drops must be illuminated directly by the sunlight for the rainbow to be visible.  In this image the rainbow appears to be between Warren Wilson College (near the foot of the rainbow) and the mountains behind the base of the rainbow.  Both the foreground, where a building of WWC is visible and the immediate background mountains as well as the rain are all lit up by direct sunshine. The picture at right shows a zoomed-in photo of the base of the rainbow.  The colors are extremely brilliant!  All the colors from red to blue are shown in this photo.  Notice

Physics Photo of the Week November 3, 2023 Moon's Shadow - Images from NASA GOES* This color satellite image (from NASA GOES image viewer ) was taken on October 14, 2023 during the partial solar eclipse (see PPOW for October 17, 2023 ).  Notice that there is no land visible in the bottom left part of the image covering parts of the American southwest.  The clouds in the upper right of the image are bright white, while the clouds near the edge of the darkest regions are tinted red.  From parts of the lower left part of the image the Moon was covering the maximum amount of the Sun's apparent disk as possible.  For this eclipse the Moon was too far away from Earth to completely cover the Sun's apparent disk, but left a narrow ring of Sun exposed.  This was an annular eclipse.  Some thin clouds are barely visible in southeast Colorado illuminated by the narrow annulus of the maximally-eclipsed Sun. Why do the clouds close to the darkest regions of the photograph have a red ting