Do photons behave in all mechanical essentials just like any other particles of physics?
344021
No. Photons are not particles but may behave like particles in certain circumstances. The most commom interactions are photoelectric, Compton, and pair production in the higher energies. And like visible and near-visible light in the lower energies.\n\nParticles have none of these characteristic mechanics except their collisions which are similar to Compton collisions.
891226
anything can happen  in quantum mechanics
624084
tut_einstein has the right idea here. A photon is an element that has no rest mass, and rest mass is what we speak of when talking about mass. But while traveling around at the speed of light it contributes to objects as if it does have mass. This is the relativistic mass that people are talking off. A photon though by definition and experiment is a massless entity. That doesnt mean it can't contribute to momentum and other forces. \n\nE=mc^2 is an equation that comes out of study of Einstein's theory of special relativity. This is meant to determine the conversion of energy into mass and vice versa. \n\nTaken from wikipedia:\nConversely, a single photon travelling in empty space cannot be considered to have an effective mass, m, according to the above equation. The reason is that such a photon cannot be measured in any way to be at "rest" and the formula above applies only to single particles when they are at rest. Photons are generally considered to be "massless," (i.e., they have no rest mass or invariant mass) even though they have varying amounts of energy.\n\nPhoton's cannot have mass because they cannot be at rest. The equation E=MC^2 as I have stated only applys to objects at rest. The total energy of a moving body is different it is calculated using the formula:\nE=(mc^2)/sqrt(1-v^2/c^2). If you solve for relative mass you can get the equation that E=m(realtice)c^2 and this equation is good for all particles moving or non moving. \n\nSo to sum it all up. A photon has no rest mass although it certainly has a relativistic mass when it is zipping through space at the speed of light.\n\nI hope that made sense
66479
No Way Man!  Photon-photon scattering?  Highly dubious.  Photons don't have charge. They don't self-interact, that's why the electro-weak theory works so well... right?\n\nResponse to Dr. Bob's response:\n\nI agree that this process occurs (although a photon that decays into a e+e- pair has to be close to another mass so momentum can be transfered; isolated photons cant decay into e+e-).  But in such a case, would you really say that "one light ray has bounced off another?" I'd say that it was "bouncing" off the electron/positron pairs.  Just semantics I suppose.
1017395
A photon is a quantum of the vibrational energy of the space grid (as in the image above). At any one point on the wave, photons are produced out of the zero-point and then oppositely, photon holes are produced. Hence, it must be the case that these oscillations up and down come in discrete steps--or quanta.\n\n \n\nWhen a particle from the quantum vacuum acquires energy from a charged particle of matter, it may expand from the addition of this excitation energy to become an ordinary photon. Energy, therefore, expands the size of a virtual photon in ground state.\n\n \n\nA virtual photon, thus, is a "collapsed" short-range quantum that becomes an ordinary photon when given energy from an excited charged particle. Hence, the primary reason that we do not observe the photons that exist in the quantum vacuum, is because the quanta of space-time that compose the vacuum have a very minute amount of energy within them and are, therefore, too small to be observed directly. However, such vacuum quanta may become observable and measurable as ordinary photons after emission.\n\n \n\nWhen actualization takes place, we may measure photons and photonic energy hitting a measuring device.  But, while in-flight, we may not speak about photons at all, because technically speaking they are not photons.  So, when Planck's equation says that energy comes in lumps E = hf, this only refers to a state of an EM wave after an actualization or measurement has happened.  Prior to this we have only Kant's noumenal "wave" condition.  \n\nphotons must have higher frequencies, by exactly one hertz, than the expected difference of the energy levels of the electrons from which they received energy. Additionally, photon wavelengths must include a very long 3 x 10^8 meters to be added to all emitted wave fronts
648100
CIH is spot on, but you should also realise from what he said that electromagnetic waves or particles are ways of describing and calculating what a photon will do, they are not the actual photon itself (whatever that is). \n\nSometimes it easy to think that the description of an object IS the object, especially if it fits it well. If it was possible to write an equation or model which fully described a motor vehicle, you still wouldn't be able to drive it to the shops, but you would be able to accurately descibe how it drove there.\n\nIsn't physics wonderful! Philosopy and science all neatly wrapped up in one unifying theory of lots of theories!
504427
Actualy, I am an expert in this field, having a Ph.D. in Optical Sciences.\n\nI don't believe light is a particle, exactly.  It is a quantization of energy, but not really like a particle.  If it were a particle it would explain how it can propagate across nothingness.  The existence of something in space would just get into its way, so the nothingness only helps light to propagate.  But a particle implies rest mass and other physical properties which light does not have.\n\nI don't believe that empty space is something, contrary to the way some people interpret Einstein.\n\nI don't believe it is action at a distance.  Light takes a finite amount of time to cross space.  The action occurs where the light is.\n\nThe question was more of a problem when light was considered to be merely a wave.  A wave needed a medium to disturb or propagate across.  Sound moves molecules about as it propagates.  But light only bears a resemblance to a wave in the way it behaves.  It is not like a classical wave.\n\nThe best way I can think of to explain it is to understand that an electromagnetic wave carries with it its own medium.  The electric and magnetic fields oscillate, feeding on itself, so to speak.  The energy is launched into space and perpetuates itself according to the laws of physics.
36613
it doesnt satisfy the qualities of being a matter, like having mass and volume, but it does have particles called photons, light behaves like a particle at times and sometimes as a wave
374885
The answer is no. Isaac Newton had assumed that light was made up of numerous small particles, in order to explain features such as its ability to travel in straight lines and reflect off surfaces. This theory was known to have its problems; although it explained reflection well, its explanation of refraction and diffraction was less pleasing. In order to explain refraction, in fact, Newton's Opticks (1704) postulated an "Aethereal Medium" transmitting vibrations faster than light, by which light (when overtaken) is put into "Fits of easy Reflexion and easy Transmission" (causing refraction and diffraction). Newton believed that these vibrations were related to things like heat radiation, saying:\n\nIs not the Heat of the warm Room convey'd through the Vacuum by the Vibrations of a much subtiler Medium than Air, which after the Air was drawn out remained in the Vacuum? And is not this Medium the same with that Medium by which Light is refracted and reflected, and by whose Vibrations Light communicates Heat to Bodies, and is put into Fits of easy Reflexion and easy Transmission? \nThe modern understanding, of course, is that heat radiation is light, but Newton considered them two different phenomena (believing heat vibrations to be excited "when a Ray of Light falls upon the Surface of any pellucid Body"). He wrote that "I do not know what this Aether is", but that if it consists of particles then they must be "exceedingly smaller than those of Air, or even than those of Light: The exceeding smallness of its Particles may contribute to the greatness of the force by which those Particles may recede from one another, and thereby make that Medium exceedingly more rare and elastick than Air, and by consequence exceedingly less able to resist the motions of Projectiles, and exceedingly more able to press upon gross Bodies, by endeavoring to expand itself."
381267
according to the theory of quantum mechanics particles can exhibit a wave like behaviour, ie particles such as electrons which fundamentally are thought of as particles can infact difract and behave like a wave. for more info look up the wave-particle duality.
952119
The photon has zero mass (it does, however, have rest mass - as in M=E/C^2). \n\nLike all quanta, the photon exhibits wave and particle properties. \n\nIt is important to remember that mass and energy are equivalent. A photon is only referred to as a particle because of certain properties that light exhibits - the "particle" is actually no more than a quanta of pure light energy - and, as such, is indeed dimensionless in the conventional sense of density and volume.
850332
Light does not consist of proton, it consists of photons which are quantum of electromagnetic radiation, photons have their own antiparticle. Antiparticle is a particle that has the same mass of another particle but its other properties are opposite which result in cancelling the opposite properties. The net result is the production of radiant energy which is light (not according to me, but according to quantum theory). So no question of mass.\n\nAnd light has very high but not infinity velocity, then how would the mass (do not say weight, both are different) be infinite (even if we consider what you say to be true)\n\nProtons are not insignificant, they make up about half the mass of an atom (under normal conditions)
1039444
No, there would be no interference pattern if light were behaving strictly as a particle.  If light acted only as a particle, the pattern seen behind two slits would be the superposition of the patterns seen behind two single slits.  That is, if light acted only as a particle, then you should see the same pattern whether you let light pass through two slits for five minutes, or whether you opened only one slit for five minutes, then closed that slit and opened the other for five minutes.\n\nOpening one slit at a time produces no interference pattern, leaving both slits open produces an interference pattern.  This cannot be explained by assuming a strictly particle interpretation of light.\n\n==============\n\nComment on "Additional Details #1"\n\nParticles of light have never been observed to bounce from one another.  Quantum electrodynamics predicts that they should, but the effect is so slight, and the probability so low, that there has never to my knowledge been a successful measurement of photon-photon scattering in the laboratory.  If the interference patterns in a Young's two-slit apparatus were to be explained by particles of light bouncing off one another, it would imply that light scatters from light very, very easily.  Crossing two flashlight beams would produce a diffuse glow from the area of intersection, and the beams would not continue onward to the places they were pointed.  We don't see that happening.  Another example:  if somebody is driving toward you with their headlights on, you cannot reduce the amount of light hitting your eyes by shining your headlights at them and deflecting their beam.
159391
We say that a photon is massless because it is in the usualy meaning of the word.  A photon has zero rest mass.  However, since it obviously has energy, it has a momentum.\n\nRead through this site and some of the related articles, I think it explains it very well,\nhttp://math.ucr.edu/home/baez/physics/ParticleAndNuclear/photon_mass.html
122851
Photons are produced by atoms when a bound electron moves from one orbital to another orbital with less energy. Photons can also be emitted by an unstable nucleus when it undergoes some types of nuclear decay. Furthermore, photons are produced whenever charged particles are accelerated.\n\nIn physics, the photon (from Greek φως, "phōs", meaning light) is the quantum of the electromagnetic field, for instance light. The term photon was coined by Gilbert Lewis in 1926.\n\n \nThe photon can be perceived as a wave or a particle, depending on how it is measuredThe photon is one of the elementary particles. Its interactions with electrons and atomic nuclei account for a great many of the features of matter, such as the existence and stability of atoms, molecules, and solids. These interactions are studied in quantum electrodynamics (QED), which is the oldest part of the Standard Model of particle physics.\n\nIn some respects a photon acts as a particle, for instance when registered by the light sensitive device in a camera. In other respects, a photon acts like a wave, as when passing through the optics in a camera. According to the so-called wave-particle duality in quantum physics, it is natural for the photon to display either aspect of its nature, according to the circumstances. Normally, light is formed from a large number of photons, with the intensity related to the number of them. At low intensity, it requires very sensitive instruments, used in astronomy or spectroscopy, for instance, to detect the individual photons.\n\nPhotons are commonly associated with visible light, but this is actually only a very limited part of the electromagnetic spectrum. All electromagnetic radiation is quantized as photons: that is, the smallest amount of electromagnetic radiation that can exist is one photon, whatever its wavelength, frequency, energy, or momentum. Photons are fundamental particles. They can be created and destroyed when interacting with other particles, but are not known to decay on their own.\n\nPhotons have zero mass and zero electric charge, but they do carry energy, momentum and angular momentum. Photons are always moving, and photons in a vacuum always move at the vacuum speed of light with respect to all observers, even when those observers are themselves moving. The energy and momentum carried by a photon is proportional to its frequency (or inversely proportional to its wavelength). This momentum can be transferred when a photon collides with matter. The force due to a large number of photons falling on a surface is known as radiation pressure, which may be used for propulsion with a solar sail.\n\nThe actual upper limit of the photon rest mass compatible with observations depends on additional assumptions. A conservative consensus limit of the Particle Data Group is 6×10-17 eV based on changes in magnetohydrodynamics which would contradict solar wind observations.\n\nPhotons are deflected by a gravitational field twice as much as Newtonian mechanics predicts for a mass traveling at the speed of light with the same momentum as the photon. This observation is commonly cited as evidence supporting Einstein's theory of gravitation, general relativity. In general relativity, photons always travel in a "straight" line, after taking into account the curvature of spacetime. (In curved space, such lines are called geodesics).
514677
In many cases, people may say a photon "sometimes acts like a wave and sometimes acts like a particle". This is slightly misleading, because a photon always acts like both. For example, when shooting single photons through a slit, a detector can detect each photon when it hits — but over time, the detector will detect the same diffraction pattern as it would if the photons were given off all in one burst. This is because any given trajectory the photon could take has a certain probability that is dictated by the properties of an electromagnetic wave.
372933
A photon will keep going until it gets absorbed.  By the essense of your question, I am guessing that you are thinking of photons in terms of a solid particle.  True, it can be thought of as a particle, that is part of wave-particle duality.  But the truth is, we cannot really understand wave-particle duality in an intuitive way.  The mathematics are well understood, but as humans we cannot really grasp, it does not make sense to our everyday experiences.  Don't think of it as a particle disappearing.  A photon is merely a means of transmitting energy.\n\nMaybe this will help:  An atom is in an energized state with an electron in a higher orbital.  The electron drops to the ground state and a photon is emitted.  That photon travels either 10 nanometers or one light year (doesn't matter) until it interacts with another atom of the same kind.  That second atom absorbs the photon and an electron gets excited to the same state as the electron in the orginal atom.  So in this sense a photon is just a means of transferring energy.  No matter is created or destroyed.