Physics Photo of the Week

  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 energy of the ball excavated

  Video made with the slo-mo application of my smart phone, and played back at 2 frames per second.

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 distant shore, especially close

  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 brighter clouds at the leading part o

  Eclipse 2024 from Northeast Vermont - P hotos  by Olivia Mitchell-Eby The recent total solar eclipse was spectacular for family kin in a corner of Vermont called the "Northeast Kingdom".  Olivia used her cell phone held in her lap to take photos of the on-coming eclipse.  In the distance above the horizon we can see the on-coming ominous shadow of the Moon approaching Olivia and her immediate family amidst new-fallen snow.  The fresh snow is a sign of Vermont spring in early April. Modern cell phones have the a bility to do time-lapse videos, so Olivia supported her cell phone in here lap aimed at the eclipsing su n and recorded the time-lapse video seen below.     This video is amazing.  We can see the Moon's shadow projected on the thin cirrus clouds, when the shadow arrives at the viewing point, the sky becomes dark.  We don't see the Sun as if it were eclipsed however.  Cell phones are "smart" and set the exposures automatically.  When the sky turned

Totality! April 8, 2024 - Photo by Donald F. Collins We traveled to Shaker Heights, Ohio (next to Cleveland) to capture the total solar eclipse.  We woke up to some rain and solid clouds as a cold front passed through, but the front passed with beautiful clear skies by noon.  The totality began about 3:13 pm and lasted 3 min:49 sec. The total solar eclipse is characterized by the corona - the halo immediately surrounding the Sun.  The corona consists of ionized gases ejected from the surface of the Sun which glow with the spectra characteristic of the the elements in the Sun.  The shape of the corona is variable from eclipse to eclipse causing every solar eclipse to produce a different display.  The corona is also strongly shaped by the strong magnetic fields surrounding the Sun.  The eclipse also shows several solar prominences - the flame-like ejections of solar mater being "boiled" off into space.  The prominence protruding from the south limb (the bottom edge of the pho