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Physics Photo of the Week - Sept. 27, 2024

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  Physics of a splash of water This week's photo shows details of the splash observed when a tennis ball was thrown into a body of water.  The ball was thrown from someone on shore when a slo-mo video was recorded on a smart phone.  This is the first video frame immediately after the ball landed in the water.  The immediate reaction from the water is the ejection of a crown-shaped splash that we see in the photo.     A few frames later we can see the rebound effect sending a long column of water shooting up from the splash area as a rebound effect of the water - seen in the photo at right. Click on either of the images to view a slo-mo video of the ball approaching the water, the immediate crown effect, then the spout of water as a result of the rebound of the water as the water rushed back into the sizable cavity made by the ball when it hit the water from a height of a few meters. Examining the slo-mo video frame-by-frame we can see that the kinetic ener...
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Physics Photo of the Week Reflections and Mirages

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Physics Photo of the Week  September 13, 2024 Reflections and Mirages Lakes are always very photogenic when the mountains and other objects are reflected in the water.  However, there are two kinds of reflections in this week's photo, although only one kind of reflection (the direct simple reflection) is seen.  We first notice the reflection of the diving platform close by and the prominent reflection of the background mountain, Mt. Hor, that overlooks Willoughby Lake in Vermont.   The images below show a close-up of the raft and a close-up of the more distant shore of the lake from the left center part of the photo:   The reflections from the close-up of the raft are clear, however the raft's reflections are distorted by the small ripples of the water surface.  The reflections of the background trees, especially the tree-tops are also distorted by the water ripples.  Somewhat like fun-house mirrors that have curved surfaces. The close-up of the dista...
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Physics Photo of the Week May 10, 2024

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  Broken Contrail Shadow - Photo by Nasuna Stuart-Ulin Betsy Warren - a PPOW reader - recently sent me a link to a NY Times article (April 15, 2024) that featured a jet's contrail shadowed on the thin clouds below the contrail.  The photo was taken on eclipse day (April 8, 2024) during the partial phase (the Sun was about 90 % blocked by the Moon). The photo has a number of interesting features: The contrail appears to lie below the thin cirrus clouds.  That is just an illusion.  The clouds are thin, and we see the contrail through the thin clouds.  The camera is looking up at the sky; the over-exposed Sun is very far away far above the sky and clouds.  In order for the contrail to cast a shadow the contrail must be above the clouds, between the clouds and theSun.  Notice also that the contrail's shadow appears broken and even doubled in the region where the two shadows overlap.  That is caused by two distinct thin layers of clouds.  The b...
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