Radioactive decay Alpha decay is one example type of radioactive decay, in which an atomic nucleus emits an alpha particle, and thereby transforms (or 'decays') into an atom with a mass number decreased by 4 and atomic number decreased by 2. Many other types of decays are possible. Radioactive decay, also known as nuclear decay or radioactivity, is the process by which a nucleus of an unstable atom loses energy by emitting particles of ionizing radiation. A material that spontaneously emits this kind of radiation—which includes the emission of energetic alpha particles, beta particles, and gamma rays—is considered radioactive. Radioactive decay is a stochastic (i.e. random) process at the level of single atoms, in that, according to quantum theory, it is impossible to predict when a particular atom will decay. However, the chance that a given atom will decay is constant over time. There are many different types of radioactive decay (see table below). Discovery and history Types of decay
Black body As the temperature of a black body decreases, its intensity also decreases and its peak moves to longer wavelengths. Shown for comparison is the classical Rayleigh–Jeans law and its ultraviolet catastrophe. A black body is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. A black body in thermal equilibrium (that is, at a constant temperature) emits electromagnetic radiation called black-body radiation. The radiation is emitted according to Planck's law, meaning that it has a spectrum that is determined by the temperature alone (see figure at right), not by the body's shape or composition. A black body in thermal equilibrium has two notable properties: It is an ideal emitter: it emits as much or more energy at every frequency than any other body at the same temperature.It is a diffuse emitter: the energy is radiated isotropically, independent of direction. Definition Idealizations Realizations
Davisson–Germer experiment History and Overview According to Maxwell's equations in the late 19th century, light was thought to consist of waves of electromagnetic fields and matter was thought to consist of localized particles. However, this was challenged in Albert Einstein’s 1905 paper on the photoelectric effect, which described light as discrete and localized quanta of energy (now called photons), which won him the Nobel Prize in Physics in 1921. In 1927 Louis de Broglie presented his thesis concerning the wave-particle duality theory, which proposed the idea that all matter displays the wave-particle duality of photons. According to de Broglie, for all matter and for radiation alike, the energy E of the particle was related to the frequency of its associated wave ν by the Planck relation: And that the momentum of the particle p was related to its wavelength by what is now known as the de Broglie relation: where h is Planck's constant. Early Experiments Experimental setup A breakthrough R.
Quantum entanglement Quantum entanglement is a physical phenomenon that occurs when pairs or groups of particles are generated or interact in ways such that the quantum state of each particle cannot be described independently – instead, a quantum state may be given for the system as a whole. Such phenomena were the subject of a 1935 paper by Albert Einstein, Boris Podolsky and Nathan Rosen, describing what came to be known as the EPR paradox, and several papers by Erwin Schrödinger shortly thereafter. Einstein and others considered such behavior to be impossible, as it violated the local realist view of causality (Einstein referred to it as "spooky action at a distance"), and argued that the accepted formulation of quantum mechanics must therefore be incomplete. History However, they did not coin the word entanglement, nor did they generalize the special properties of the state they considered. Concept Meaning of entanglement Apparent paradox The hidden variables theory
holography « LifeOS: exploring the system that executes DNA It all starts with the properties of laser light. Of course you know how a laser is created. Ordinary light is beamed through a crystal. The properties of laser light are still being explored, but those already discovered have revolutionized modern technology. What makes a hologram work is that the two beams of laser light that illuminate the object are not only the same type, but in perfect synchronization. The resulting pattern is meaningless when seen in ordinary light, but when illuminated by the original laser, it produces a 3D image of the original object. The interference patterns captured on film are not focused by a lens and therefore the information thus recorded is evenly distributed over the recording surface. Quoted from, “The Holographic Universe”, by Michael Talbot The “whole in every part” nature of a hologram provides us with an entirely new way of understanding organization and order. A Coherent Electromagnetic Field Holographic Memory More from Michael Talbot:
Thomas Young (scientist) Thomas Young (13 June 1773 – 10 May 1829) was an English polymath. Young made notable scientific contributions to the fields of vision, light, solid mechanics, energy, physiology, language, musical harmony, and Egyptology. He "made a number of original and insightful innovations" in the decipherment of Egyptian hieroglyphs (specifically the Rosetta Stone) before Jean-François Champollion eventually expanded on his work. Young belonged to a Quaker family of Milverton, Somerset, where he was born in 1773, the eldest of ten children. Young began to study medicine in London in 1792, moved to Edinburgh in 1794, and a year later went to Göttingen, Lower Saxony, Germany where he obtained the degree of doctor of physics in 1796. In 1801 Young was appointed professor of natural philosophy (mainly physics) at the Royal Institution. Thomas Young died in London on 10 May 1829, and was buried in the cemetery of St. Young was highly regarded by his friends and colleagues.
Casimir effect Casimir forces on parallel plates A water wave analogue of the Casimir effect. Two parallel plates are submerged into colored water contained in a sonicator. When the sonicator is turned on, waves are excited imitating vacuum fluctuations; as a result, the plates attract to each other. The typical example is of two uncharged metallic plates in a vacuum, placed a few nanometers apart. Dutch physicists Hendrik B. In modern theoretical physics, the Casimir effect plays an important role in the chiral bag model of the nucleon; and in applied physics, it is significant in some aspects of emerging microtechnologies and nanotechnologies. Any medium supporting oscillations has an analogue of the Casimir effect. Overview Possible causes Vacuum energy Main article: Vacuum energy Summing over all possible oscillators at all points in space gives an infinite quantity. Relativistic van der Waals force Effects . ). depends on the shape, and so one should write , at point p.
Stern–Gerlach experiment Basic theory and description Quantum spin versus classical magnet in the Stern–Gerlach experiment Basic elements of the Stern–Gerlach experiment. The Stern–Gerlach experiment involves sending a beam of particles through an inhomogeneous magnetic field and observing their deflection. The results show that particles possess an intrinsic angular momentum that is closely analogous to the angular momentum of a classically spinning object, but that takes only certain quantized values. The experiment is normally conducted using electrically neutral particles or atoms. If the experiment is conducted using charged particles like electrons, there will be a Lorentz force that tends to bend the trajectory in a circle (see cyclotron motion). Spin values for fermions. Electrons are spin-1⁄2 particles. For electrons there are two possible values for the spin angular momentum that is measured along an axis. The constants c1 and c2 are complex numbers. one of the two possible values of j is found.
First Quantum Effects Seen in Visible Object Science has proved contradiction. Unless, of course, we know that contradiction is impossible, and that the law of non-contradiction was used in the process of "proving" contradiction, making it a self-defeating argument. Now, any rational person will know that nothing can be and not be at the same time, so this whole thing is absurd on its face, unless you take it to mean both are happening in some kind of figurative, unreal sense, in which case the article is luridly, and I suspect purposefully, misleading. Take away the breaking of the law of non-contradiction. These things are unknowable until they actually occur, yet follow laws of probability? Just thought I would be polemical and challenge the smug consensus here.
Beats. From Physclips Interference and consonance The ratios 3:2 and 5:4 are called (by many Western people, at least), musical consonances (in just intonation). In this example, one tone remains constant at 400 Hz. Here are some more consonances in just intonation. and here a scale constructed using the notes used the consonances given above, plus two consonances at 5:4 and 3:2 based on the fifth note in the scale. However, this has taken us some distance from beats and Tartini tones. Tuning a guitar with beats and harmonics Here I use the fourth 'harmonic' on the low E string and the third 'harmonic' on the A string. Look at the soundtrack. In the clip above, we notice that, because of the finite ring time of the strings, there is a limit to the precision of the tuning. What beats have to do with Heisenberg's Uncertainty Principle
Henri Becquerel Antoine Henri Becquerel (15 December 1852 – 25 August 1908) was a French physicist, Nobel laureate, and the discoverer of radioactivity along with Marie Skłodowska-Curie and Pierre Curie, for which all three won the 1903 Nobel Prize in Physics. Biography Early life Becquerel was born in Paris into a family which produced four generations of scientists: Becquerel's grandfather (Antoine César Becquerel), father (Alexandre-Edmond Becquerel), and son (Jean Becquerel). Career In 1892, he became the third in his family to occupy the physics chair at the Muséum National d'Histoire Naturelle. Becquerel's earliest works centered around the subject of his doctoral thesis: the plane polarization of light, with the phenomenon of phosphorescence and absorption of light by crystals. Becquerel's discovery of spontaneous radioactivity is a famous example of serendipity, of how chance favors the prepared mind. Becquerel in the lab Honors and awards See also References
Franck–Hertz experiment Photograph of a vacuum tube with a drop of mercury that's used for the Franck–Hertz experiment in instructional laboratories. A - anode disk. G - metal mesh grid. C - cathode assembly; the cathode itself is hot, and glows orange. The Franck–Hertz experiment was the first electrical measurement to clearly show the quantum nature of atoms, and thus "transformed our understanding of the world". It was presented on April 24, 1914 to the German Physical Society in a paper by James Franck and Gustav Hertz. Franck and Hertz had designed a vacuum tube for studying energetic electrons that flew through a thin vapor of mercury atoms. These experimental results proved to be consistent with the Bohr model for atoms that had been proposed the previous year by Niels Bohr. On December 10, 1926, Franck and Hertz were awarded the 1925 Nobel Prize in Physics "for their discovery of the laws governing the impact of an electron upon an atom The experiment Effect in other gases
Bell test experiments Bell test experiments or Bell's inequality experiments are designed to demonstrate the real world existence of certain theoretical consequences of the phenomenon of entanglement in quantum mechanics which could not possibly occur according to a classical picture of the world, characterised by the notion of local realism. Under local realism, correlations between outcomes of different measurements performed on separated physical systems have to satisfy certain constraints, called Bell inequalities. John Bell derived the first inequality of this kind in his paper "On the Einstein-Podolsky-Rosen Paradox". Bell's Theorem states that the predictions of quantum mechanics cannot be reproduced by any local hidden variable theory. The term "Bell inequality" can mean any one of a number of inequalities satisfied by local hidden variables theories; in practice, in present day experiments, most often the CHSH; earlier the CH74 inequality. Conduct of optical Bell test experiments Pan et al.'
Bell's theorem Bell's theorem is a no-go theorem famous for drawing an important distinction between quantum mechanics (QM) and the world as described by classical mechanics. In its simplest form, Bell's theorem states: No physical theory of local hidden variables can ever reproduce all of the predictions of quantum mechanics. In the early 1930s, the philosophical implications of the current interpretations of quantum theory were troubling to many prominent physicists of the day, including Albert Einstein. In a well-known 1935 paper, Einstein and co-authors Boris Podolsky and Nathan Rosen (collectively "EPR") demonstrated by a paradox that QM was incomplete. This provided hope that a more-complete (and less-troubling) theory might one day be discovered. In the 1950s, antecedent probabilistic theorems were published by Jean Bass, Emil D. These three key concepts – locality, realism, freedom – are highly technical and much debated. Overview , local realism predicts or less. Bell inequalities