Topic: quantum electrodynamics

topics > Group: science

atoms and molecules
electricity and magnetism
electromagnetic field
physics as computation
quantum mechanics
science as mathematics
Subtopic: electrodynamics up

Quote: quantum electrodynamics describes all physical phenomena except gravity, radioactivity and nuclear physics; there is no significant difference between experiment and theory [»feynRP_1985]
Quote: derive standard results of electromagnetic theory from macroscopic quantum systems; without Maxwell's equations, traditional quantum formalisms, or correspondence limits [»meadCA6_1997]
Quote: all electrical and light phenomena arise from photons and electrons moving from place to place and from electrons emitting and absorbing photons [»feynRP_1985]
Quote: derive standard results of electromagnetic theory from macroscopic quantum systems; without Maxwell's equations, traditional quantum formalisms, or correspondence limits [»meadCA6_1997]
Quote: use vector and scalar potentials for introducing electromagnetic effects into quantum descriptions; avoids the use of force concepts
Quote: classically, the minimum energy for positive and negative charges in a collection of atoms is all on top of each other; this was a puzzle
Quote: Shrodinger's equation for a electron moving in a line through free space is the same as the limiting case of an electron moving along a line of atoms [»feynRP_1965]
Quote: Schrodinger's equation of an electron moving freely in space provided a theory for calculating atomic phenomena accurately and in detail [»feynRP_1965]
Quote: the mathematics of Schrodinger's equation soon becomes too complicated to solve exactly any but the simplest problems
Quote: Dirac discovered the correct relativistic equation for the motion of an electron a year after Schrodinger's discovery; needed for magnetism [»feynRP_1965]

Subtopic: probablistic up

Quote: Nature herself does not even known which way the electron is going to go; intrinsically probabilistic [»feynR_1965]
Quote: quantum electrodynamics describes Nature as absurd
Quote: each event in quantum electrodynamics has a probability amplitude; compute from the ways the event could have happened
Quote: physics students often identify a photon with the arrow that represents the probability amplitude; but these arrows only define the probability of an event [»feynRP_1985]

Subtopic: field up

Quote: a magnetic or electrical field changes the phase of the probability amplitude to arrive via any trajectory by the space or time integrals respectively [»feynRP_1964]

Subtopic: photon up

Quote: light consists of a finite number of energy quanta localized in space; moving without dividing; absorbed or generated only as complete units
Quote: the energy of light is discontinuously distributed in space; e.g., black-body radiation and photoluminesce [»einsA3_1905]
Quote: light is made of particles called photons; can be individually detected [»feynRP_1985]
Quote: a photon behaves in a wavelike way entirely on its own; its alternative possibilities can cancel out [»penrR_1989]
Quote: the number of photons in a particular state is the same concept as the number of the energy level associated with a particular mode of oscillation of the electromagnetic field

Subtopic: electron up

Quote: electrons behave like photons; on a large scale they travel like particles; inside an atom, there is no orbit, only all sorts of ways that the electron could go along with a probability amplitude for each way [»feynRP_1985]
Quote: an electron is kept within a certain range of the nucleus by photon exchanges with protons [»feynRP_1985]

Subtopic: light up

Quote: light scatters when a photon is absorbed and then re-emitted [»feynRP_1965]
Quote: the quantum theory of light scattering gives the same result as the classical theory where an electron acts as a linear oscillator

Subtopic: reflection up

Quote: consider reflection of a beam of electrons at a grating; if we know where an electron hits, its velocity must be so high that its de Broglie wavelength is much smaller than the grating, yielding classical reflection [»heisW_1927]
Quote: light appears to reflect from one point of a mirror because that is where many possible paths take nearly equal time [»feynRP_1985]
Quote: light doesn't only travel in a straight line; it "smells" the neighboring paths through a small core of nearby space; e.g., a very small mirror scatters light instead of reflecting it [»feynRP_1985]
Quote: light is scattered by the electrons inside a piece of glass and new photons are emitted; equivalent to back- and front-surface reflections [»feynRP_1985]

Subtopic: speed of light up

Quote: can remove the speed of light from physical equations by defining the unit of time as the time in which light travels 1cm [»einsA_1949]

Subtopic: life up

Quote: preparing two electrons in the same state is equivalent to breeding two ducks with the same heredity [»thomR_1975]
Quote: life may depend on the individuality of a quantum of action, associated with some amplifying mechanism
Quote: life and the quantum of action are elementary facts; it may be impossible to investigate life at the atomic level without killing the organism [»bohrN8_1932]
Quote: 5 or 6 photons will activate an eye's nerve cell; if a single photon, would see flashes of equal intensity, i.e., particles [»feynRP_1985]

Subtopic: organic molecules up

Quote: when light strikes strongly absorbing organic substances (e.g., rhodopsin), all electrons shift by one double bond; effectively moving an electron the width of the molecule

Related Topics up

Topic: atoms and molecules (57 items)
Topic: chemistry (11 items)
Topic: electricity and magnetism (53 items)
Topic: electromagnetic field (63 items)
Topic: light (46 items)
Topic: physics (51 items)
Topic: physics as computation (31 items)
Topic: quantum mechanics (103 items)
Topic: science as mathematics
(26 items)

Updated barberCB 10/05
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