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