Two opposing waves combine to form a standing wave. For waves of equal amplitude traveling in opposing directions, there is on average no net propagation of energy. Moving medium As an example of the first type, under certain meteorological conditions standing waves form in the atmosphere in the lee of mountain ranges. Such waves are often exploited by glider pilots. Standing waves and hydraulic jumps also form on fast flowing river rapids and tidal currents such as the Saltstraumen maelstrom. Opposing waves In practice, losses in the transmission line and other components mean that a perfect reflection and a pure standing wave are never achieved. Another example is standing waves in the open ocean formed by waves with the same wave period moving in opposite directions. Mathematical description In one dimension, two waves with the same frequency, wavelength and amplitude traveling in opposite directions will interfere and produce a standing wave or stationary wave. and
Related: Standing waves
Extremely low frequency1982 aerial view of the U.S. Navy Clam Lake, Wisconsin ELF transmitter facility, used to communicate with deeply submerged submarines. Extremely low frequency (ELF) is the ITU designation for electromagnetic radiation (radio waves) with frequencies from 3 to 30 Hz, and corresponding wavelengths from 100,000 to 10,000 kilometers. In atmospheric science, an alternative definition is usually given, from 3 Hz to 3 kHz. In the related magnetosphere science, the lower frequency electromagnetic oscillations (pulsations occurring below ~3 Hz) are considered to lie in the ULF range, which is thus also defined differently from the ITU radio bands. Alternate definitions Military communications Explanation Because of its electrical conductivity, seawater shields submarines from most higher frequency radio waves, making radio communication with submerged submarines at ordinary frequencies impossible. Difficulties of ELF communication Ecological impact
Scalar energyIf either of the major scalar weapon armed countries e.g. U.S. or Russia were to fire a nuclear missile to attack each other, this may possibly not even reach the target because the missile could be destroyed with scalar technology before it even left its place or origin. The knowledge via radio waves that it was about to be fired could be eavesdropped and the target could be destroyed in the bunker, fired at from space by satellite. Alternatively, invisible moving barriers and globes made of plasma (produced by crossed scalar beams) could destroy any nuclear missile easily while it moves towards the target and failing all these, it could be destroyed by entering the target's territory by passing through a Tesla shield which would explode anything entering its airspace. To begin with, defense using scalar technology could intercept it before it even landed. Tesla globes could also activate a missile's nuclear warhead en route by creating a violent low order nuclear explosion.
Optics on the WebLinks to optics-related applets, tutorials and web sites of interest. NOTE: Some applets no longer work with the most recent Java. If possible, try running on an earlier version. In some cases, I've found alternate applets that are similar and that will run on most browsers (I use Chrome, Safari and Firefox). If you find a link that doesn't work, please email me. Applications of Optics in Communications (Fiber Optics), Manufacturing, Medicine (including the eye) and More Societies, Organizations and Online Magazines This site contains a huge collection of tutorials and applets covering most of an introductory optics course. This is an optics tutorial for chemistry students. optics tutorial with an ophthalmic slant, including how corrective lenses work
page2WHAT IS THIRD SOUND? Superfluids Speed of a Third Sound Wave Two-fluid hydrodynamics What's it good for? Sound modes in bulk liquid For more information Third sound References Superfluids Water flowing down a pipe experiences viscous drag, which causes it to lose energy and slow down. Liquid helium (both 3He and 4He) and the electrons in a superconductor, have the amazing property that they can flow without this energy loss. Normal fluid near a wall, such as the substrate above, tends to move with the wall.
Twisted light beats quantum lightThe cool thing about science is that, even in the areas that you think you are pretty knowledgeable, surprises abound. This is what keeps me turning up to work (occasionally) and (even more occasionally) committing the crime of science writing. In this case, I get to combine a work interest (using light to measure stuff) with one of last century's passing fads (light with orbital angular momentum). I'm being a little unfair to the community of researchers who play with twisted light. In the '90s, twisted light was a big deal. In many types of optical measurements, we rely on the accurate alignment of two coordinate systems. Polarization is a measurement that tells us about the spatial orientation of the electromagnetic field of the light and how it evolves in time. When we measure polarization, however, we use apparatuses that measure the intensity of light after it has been filtered at a specific orientation. This sounds promising then. Light that is... twisted
String theoryString theory was first studied in the late 1960s as a theory of the strong nuclear force before being abandoned in favor of the theory of quantum chromodynamics. Subsequently, it was realized that the very properties that made string theory unsuitable as a theory of nuclear physics made it a promising candidate for a quantum theory of gravity. Five consistent versions of string theory were developed until it was realized in the mid-1990s that they were different limits of a conjectured single 11-dimensional theory now known as M-theory. Many theoretical physicists, including Stephen Hawking, Edward Witten and Juan Maldacena, believe that string theory is a step towards the correct fundamental description of nature: it accommodates a consistent combination of quantum field theory and general relativity, agrees with insights in quantum gravity (such as the holographic principle and black hole thermodynamics) and has passed many non-trivial checks of its internal consistency.
Les ondes stationnaires d'IvanovVous trouverez ci-dessous une expérience très intéressante. Elle montre toutes les propriétés des "ondes d'Ivanov" en un seul jet. Puisque la matière est faite d'ondes stationnaires, une telle expérience s'imposait. Standing_Waves_06_Doppler.mkv Je vous rappelle que vous pouvez télécharger les programmes que j'ai écrits dans le but de produire ces séquences en les repérant dans l'un des répertoires ci-dessous, que j'ai rendus publics. Programmes Programs Vidéos Il s'agit véritablement d'une expérience puisque j'ai eu recours au médium virtuel Delmotte-Marcotte pour obtenir l'effet Doppler. Faut-il rappeler que la matière présente manifestement des propriétés ondulatoires et que Louis de Broglie a parlé d'ondes stationnaires? L'origine du facteur de contraction de Lorentz. On sait que la fameuse "aberration" dont parle abondamment Henri Poincaré, qui fut le fer de lance de la théorie de Lorentz, est une découverte de Michelson bien antérieure à 1887. Ci-dessous, M. Un hommage à M.
Interference (wave propagation)Swimming Pool Interference Interference of waves from two point sources. Magnified-image of coloured interference-pattern in soap-film. The black "holes" are areas where the film is very thin and there is a nearly total destructive interference. Consider, for example, what happens when two identical stones are dropped into a still pool of water at different locations. Geometrical arrangement for two plane wave interference Interference fringes in overlapping plane waves A simple form of interference pattern is obtained if two plane waves of the same frequency intersect at an angle. It can be seen that the two waves are in phase when and are half a cycle out of phase when Constructive interference occurs when the waves are in phase, and destructive interference when they are half a cycle out of phase. and df is known as the fringe spacing. The fringes are observed wherever the two waves overlap and the fringe spacing is uniform throughout. A point source produces a spherical wave. for to where
Effet Magnus et turbulence dans le footballUn article de Wikipédia, l'encyclopédie libre. L'effet Magnus et la turbulence sont deux effets aérodynamiques qui interviennent dans certaines frappes de ballon au football. On parle parfois d'« effet Carlos-Magnus-Bernoulli ». Au football, un type de frappe de balle dite « frappe enveloppée » vise à donner une trajectoire courbe au ballon. Ce type de frappe est souvent utilisé lors des tirs de coup francs pour contourner le mur défensif constitué par une rangée de joueurs adverses placés entre le ballon et le but et faire revenir le ballon vers le but. Cette frappe, en faisant tournoyer le ballon sur lui-même, lui donne un effet qui modifie sa trajectoire pendant sa course. Exemple célèbre[modifier | modifier le code] Coup franc de Roberto Carlos : position des joueurs et trajectoires. Cet exemple particulièrement célèbre a été étudié et expliqué par des physiciens des fluides. Problème[modifier | modifier le code] Analyse[modifier | modifier le code]