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Quantum electrodynamics

Quantum electrodynamics
In particle physics, quantum electrodynamics (QED) is the relativistic quantum field theory of electrodynamics. In essence, it describes how light and matter interact and is the first theory where full agreement between quantum mechanics and special relativity is achieved. QED mathematically describes all phenomena involving electrically charged particles interacting by means of exchange of photons and represents the quantum counterpart of classical electromagnetism giving a complete account of matter and light interaction. History[edit] The first formulation of a quantum theory describing radiation and matter interaction is attributed to British scientist Paul Dirac, who (during the 1920s) was first able to compute the coefficient of spontaneous emission of an atom.[2] Difficulties with the theory increased through the end of 1940. QED has served as the model and template for all subsequent quantum field theories. Feynman's view of quantum electrodynamics[edit] Introduction[edit] or Related:  Leseliste

The most ridiculous job interview questions As if job interviews weren't stressful enough, hiring managers at some of the largest companies have taken to throwing real curve balls. Here's a sampling of the wackiest questions. By Anne Fisher, contributor FORTUNE -- With about five candidates for every job opening these days, some responsible for hiring decisions have resorted to desperate measures in their efforts to narrow the field. culled through tens of thousands of queries reported by job seekers who had done their best to come up with answers on the spot, and selected the oddest interview questions of the past 15 months. Luckily for beleaguered candidates, the interviewers seemed in most cases to be more interested in how people responded -- that is, in hearing their thought process, and seeing how well they kept their cool -- than in receiving a "correct" response. "Using a scale of 1 to 10, rate yourself on how weird you are." -- Capital One (COF) "How many balloons would fit in this room?" Also on

Vector From Wikipedia, the free encyclopedia Vector may refer to: In mathematics and physics[edit] In computer science[edit] In biology[edit] In business[edit] In entertainment[edit] Fictional characters and elements[edit] Other uses[edit] See also[edit] Facing awkward job interview questions Some potential employers knowingly ask candidates bizarre questions too see how they react. Certain topics interviewer cannot broach, but awkward questions may still be askedYou can always toss an awkward question back at the interviewerYou can also ignore the question by acknowledging it and quickly moving onto another subjectRemember that an interview is a two-way street. You're also deciding if you want them (CNN) -- With the economy picking up and college graduation season upon us, job interviews are on the rise. Those of you making the interview rounds may not realize that the law bars prospective employers from asking certain questions. Before former Oklahoma State wide receiver Dez Bryant was drafted into the NFL last month to play for the Dallas Cowboys he was asked one such inappropriate question. Ireland later apologized. Bryant had stated during the pre-draft interview that his father was a pimp and that his mother worked for him.

Electric field Electric field lines emanating from a point positive electric charge suspended over an infinite sheet of conducting material. Qualitative description[edit] An electric field that changes with time, such as due to the motion of charged particles producing the field, influences the local magnetic field. That is: the electric and magnetic fields are not separate phenomena; what one observer perceives as an electric field, another observer in a different frame of reference perceives as a mixture of electric and magnetic fields. For this reason, one speaks of "electromagnetism" or "electromagnetic fields". In quantum electrodynamics, disturbances in the electromagnetic fields are called photons. Definition[edit] Electric Field[edit] Consider a point charge q with position (x,y,z). Notice that the magnitude of the electric field has dimensions of Force/Charge. Superposition[edit] Array of discrete point charges[edit] Electric fields satisfy the superposition principle. Continuum of charges[edit]

Ace the odd interview questions No matter how odd the question, answer in a way that reflects best on your personality. Hiring managers veer from traditional interview questions to pick up on personality traitscompanies want people who can help the business prosper in a tough economic environmentNo matter the question, what you say should be tied to your qualifications for the position ( -- Turns out that job seekers are not the only ones getting creative in the interview process. A new CareerBuilder survey of hiring managers revealed that they, too, are starting to veer from the traditional interview questions in order to get candidates to offer up even more unique glimpses into their personality. According to the latest Job Openings and Labor Turnover Survey (JOLTS) conducted by the Bureau of Labor Statistics, the number of applicants competing for every job opening in the U.S. is double the historic norm at seven candidates per opening. Q: Do you believe in UFOS? Let's be honest -- everyone has.

Dimensional analysis Dimensional analysis is routinely used as a check on the plausibility of derived equations and computations. It is also used to categorize types of physical quantities and units based on their relationship to or dependence on other units. Great principle of similitude[edit] The basic principle of dimensional analysis was known to Isaac Newton (1686) who referred to it as the "Great Principle of Similitude".[1] James Clerk Maxwell played a major role in establishing modern use of dimensional analysis by distinguishing mass, length, and time as fundamental units, while referring to other units as derived.[2] The 19th-century French mathematician Joseph Fourier made important contributions[3] based on the idea that physical laws like F = ma should be independent of the units employed to measure the physical variables. Definition[edit] The term dimension is more abstract than scale unit: mass is a dimension, while kilograms are a scale unit (choice of standard) in the mass dimension.

5 Things I Look for in a Great Job Interview In my career I have reviewed thousands of resumes and conducted hundreds of employment interviews for both The Trademark Company and other businesses for which I have worked. In doing so, I got to see the good, the bad, and the downright ugly in terms of resumes, interviewing skills, and the like. For other CEOs looking to hire, here's what I think makes a great candidate stand out from the good ones. 1. Attention to detail How many times have you heard this one, right? There’s a great story at the end of the movie Coming to America with Eddie Murphy. A man goes into a restaurant. At this point you may be asking yourself, “So what does this have to do with identifying a great candidate?” Not less than two months ago I received a wonderful e-mail from an applicant seeking to work for The Trademark Company. The applicant had failed to attach a resume. Some CEOs may have overlooked this and just asked for the resume. 2. 3. 4. 5. Let’s take one of my more infamous examples.

Tests of special relativity Special relativity is a physical theory that plays a fundamental role in the description of all physical phenomena, as long as gravitation is not significant. Many experiments played (and still play) an important role in its development and justification. The strength of the theory lies in its unique ability to correctly predict to high precision the outcome of an extremely diverse range of experiments. Repeats of many of those experiments are still being conducted with steadily increased precision, with modern experiments focusing on effects such as at the Planck scale and in the neutrino sector. Their results are consistent with the predictions of special relativity. Collections of various tests were given by Jakob Laub,[1] Zhang,[2] Mattingly,[3] Clifford Will,[4] and Roberts/Schleif.[5] Special relativity is restricted to flat spacetime, i.e., to all phenomena without significant influence of gravitation. Experiments paving the way to relativity[edit] First-order experiments[edit]

6 Signs Your Job Interview Went Well inShare921 Right after a job interview, you're going to feel pretty relieved that it's all over and either confident that you did well or worried that you bombed. It's common for job seekers to go over the job interview questions that they went through and the answers they gave, and note any other small things during the interview - but how do you really know whether or not you did well? Check out these 6 points below and you'll have a better understanding of whether or not your job interview went well. 1. They give you a firm answer about when you’ll hear back. This is not a foolproof indicator, but it’s a good one none the less. 2. A good interview is one where you handily answer all their questions, clearly demonstrate that you can meet all the job requirements, AND THEN start to discuss all the other things you can bring to the job. 3. This one is logical enough. | 1 | 2 | Next Page

Light-time correction Light-time correction is a displacement in the apparent position of a celestial object from its true position (or geometric position) caused by the object's motion during the time it takes its light to reach an observer. Light-time correction occurs in principle during the observation of any moving object, because the speed of light is finite. The magnitude and direction of the displacement in position depends upon the distance of the object from the observer and the motion of the object, and is measured at the instant at which the object's light reaches the observer. Light-time correction can be applied to any object whose distance and motion are known. Calculation[edit] A calculation of light-time correction usually involves an iterative process. Discovery[edit] The effect of the finite speed of light on observations of celestial objects was first recognised by Ole Rømer in 1675, during a series of observations of eclipses of the moons of Jupiter. References[edit] P.

Your 30 Second Commercial First impressions are extremely important when it comes to the interview process. You’ve heard this time and time again—you only have one chance to make a good first impression. Unfortunately this is all too true. When you meet someone who may give you the name of an employer who they know to be hiring or when you’re sitting with a decision maker in an interview situation, it’s important to be aware and prepared to make an excellent first impression. One way to do this is to prepare a 30-second commercial that will state your purpose, reemphasize their need and suggest your apparent desire and ability to fill that particular need. What is a commercial? There are a lot of things that need to be said in a matter of seconds without rambling but not being too vague. Here are some sentence starters that you can use: I also have a solid background in… My strengths are… I have _____ years of experience in… What then would you say in your 30 second commercial? - Donalyn Spisak

Tensor Cauchy stress tensor, a second-order tensor. The tensor's components, in a three-dimensional Cartesian coordinate system, form the matrix whose columns are the stresses (forces per unit area) acting on the e1, e2, and e3 faces of the cube. Tensors are used to represent correspondences between sets of geometric vectors. For example, the Cauchy stress tensor T takes a direction v as input and produces the stress T(v) on the surface normal to this vector for output thus expressing a relationship between these two vectors, shown in the figure (right). Because they express a relationship between vectors, tensors themselves must be independent of a particular choice of coordinate system. Tensors are important in physics because they provide a concise mathematical framework for formulating and solving physics problems in areas such as elasticity, fluid mechanics, and general relativity. Definition[edit] There are several approaches to defining tensors. As multidimensional arrays[edit] as, .

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