Light is the speed of Photon particles in an atom whereas?
455984
Photons because light travels at 300000km/s, it would be called teleportation if an human was able to travel at such a speed.
838380
Photons that travel at the speed of light have zero mass.  Photons are tiny packets of pure energy.  Theoretically photons could be converted to mass using Einstein's equation E = mc2 but would then be unable to travel at the speed of light.  Do photons really exist?  Enough of them in the UV range can give you a sunburn.
1168590
Let's look at E = mc^2.\n\nE is energy. It is measured in joules.\nm is mass. It is measured in kilograms.\nc is the speed of light. It is measured in meters per second.\n\nKilograms multiplied by (meters per second)squared are joules. If you don't have a mass multiplied by the square of a velocity (or something with equivalent units), you don't have energy.\n\nThe maximum speed any mass can have is infinitesimally less than the speed of light. c^2 would be the square of that speed.\n\nNow, let's consider the practicalities. Experimentally, we find that, as we accelerate something very close to the speed of light (which is done every day in particle accelerators, for example), it becomes harder and harder to accelerate the closer it gets to the speed of light. E = mc^2 is the energy of a mass at rest; this is where the energy of nuclear weapons and nuclear power plants comes from. As an object moves, its energy is multiplied by a factor usually abbreviated with the Greek letter gamma; its value is:\n\ngamma = 1/[1 - (v/c)^2]^1/2\n\nSo it's 1 over the square root of [1 minus (v/c)squared].\n\nAs v becomes closer and closer to the speed of light, v/c becomes closer and closer to 1, the denominator of the fraction becomes closer and closer to zero, and gamma becomes larger and larger. If v were to equal c, gamma would be infinite. This is why you can't accelerate any massive object to the speed of light - it would take an infinite amount of energy. \n\nSo, you may ask, what about photons? They go at the speed of light, don't they? Indeed they do. They manage this because their mass is zero, and they can never travel at any speed other than the speed of light.\n\nIncidentally, it is indeed true that m = E/c^2; this is often useful in physics calculations.
182197
Disregarding the pseudoscientific ramblings above, use Einstein's energy equation which states that the energy of a particle is the magnitude of its momentum 4-vector, E^2 = (mc^2)^2 - (pc)^2. Since the photon is massless, this becomes E^2 = (pc)^2, and we get the momentum of a photon as directly proportional to its energy p = E/c. \nDon't be reluctant to use the equations, and don't try to shoehorn Newtonian mechanics where it does not belong (speeds at or near the speed of light). In this case, you are using the fallacy that classical momentum mv applies to a relativistic object. For more information about similar fallacies, see the second source below.
886711
The speed of light in a vacuum is an important physical constant denoted by the letter c for constant or the Latin word celeritas meaning "swiftness". It is the speed of all electromagnetic radiation in a vacuum, not just visible light.\n\nIn metric units, c is exactly 299,792,458 metres per second (1,079,252,848.8 km/h). Note that this speed is a definition, not a measurement, since the fundamental SI unit of length, the metre, has been defined since October 21, 1983 in terms of the speed of light: one metre is the distance light travels in a vacuum in 1/299,792,458 of a second. Converted to imperial units, the speed of light is approximately 186,282.397 miles per second, or 670,616,629.384 miles per hour, or almost one foot per nanosecond.\n\nThrough any transparent or translucent material medium, like glass or air, it has a lower speed than in a vacuum; the ratio of c to this slower speed is called the refractive index of the medium (the actual speed is not affected, the speed of light is constant, the fact that the light is reflected around inside the glass will make a greater amount of time necessary for it to reach the next point). Changes of gravity, however, warp the space the light has to travel through, making it appear to curve around massive objects. This gives rise to the phenomenon of gravitational lensing, in which large assemblies of matter can refract light from far away sources, so as to produce multiple images and similar optical distortions.\nclick here:http://en.wikipedia.org/wiki/Speed_of_light#Overview
156068
Light can be thought of as both a wave and a particle.  Light particles (quanta) are called photons, and these are massless.  However, they do have a momentum.\nFor more information on photons see:\nhttp://en.wikipedia.org/wiki/Photon
59698
It is not possible to experimentally measure something to have a value of exactly zero. The current limit on the mass of the photon is < 10^25 times lighter than the proton.\n\nThe idea of a particle's mass changing with velocity has not been used by serious physicists for several decades. We now rewrite the momentum equation as\nmomentum = gamma*mass*velocity , where the factor gamma describes the effect previously known as "relativistic mass".\n\nThe energy of a particle is \nenergy = gamma * mass * c^2 (try setting gamma=1 for a stationary particle) \nso we can write momentum = energy * velocity / c^2\nor momentum = energy/c  for particles moving at the speed of light.\nSo, even though a photon has zero (or very small) mass, it still has momentum, which it can transfer to an electron.
7228
Ther are two natures assigned to light\n1.It is made of particles called photons\n2.It is an electromagnetic wave.
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).
426747
The speed of light is a measurement of how fast light travels in a vacuum. The speed of light also known as "c" as in the famous Einstein equation E=mc^2. And its equal to 299,792,458 m/s or in U.S miles per hour is about 670million miles per hour!!!!!!! It would take light coming form the sun only 8 seconds to arrive on earth which is 92million miles away. Now say "WOW!!"
144613
light rays do not move faster or slower than the speed of light.  the speed of light is the speed of light, period.\n\nthat said, light often travels *slower* than c, which is a constant defined as the speed of light IN A VACUUM, approximately 3x10^8 m/s.  here is a way you can actually observe some honest-to-god light traveling slower than c:\n\nstep 1.  find a window.\nstep 2.  look at it.\n\ncongratulations, you have observed light traveling slower than c.  in ANY medium (air, glass, water - you name it) the speed of light is slower than the speed of light in a vacuum.  \n\nin fact, the so-called index of refraction (n, which equals 1.4 for glass) is defined as the ratio of c to the speed of light in that material.  generally, denser materials have a higher index of refraction, and people have been able to make light go REALLY slow by making some very dense materials.  all of this is perfectly consistent with general relativity.\n\nas for FASTER than c:  under certain conditions, it is possible to make photons with a "phase velocity" that is greater than c.  however, when people speak of the speed of light, they usually refer to the "group velocity".  the distinction between phase velocity and group velocity is kind of technical; but phase velocity refers to the speed at which the individual phase fronts propagate through space.  \n\nit is possible to make these phase fronts go faster than c; but because the energy or information or whatever carried by the light travels at the group velocity, the actual speed (as far as stuff like general relativity is concerned) is still less than c.\n\nanyway, all of these results are entirely consistent with general relativity.  in fact, i don't know of any published results of a scientific experiment which are not consistent with GR.  \n\nthe fact that einstein's theory, largely concocted out of the blue from basic principles and logical reasoning, has stood the test of time for so many years is a testament to the genius of the man's work.\n\nhere are some links to learn about phase velocity, group velocity and the speed of light:\nhttp://en.wikipedia.org/wiki/Group_velocity\nhttp://physicsweb.org/articles/news/4/7/8/1
71955
Here are two explanations (neither particularly satisfying I will tell  you in advance.)\n\nThe first is that the speed of light (in a vaccuum) is a property of the universe that is measured the same by everyone, regardless of their motion relative to anyone else. This is a true statement born out by experiment, but it implies some very weird stuff.  One is that distance and time are not measured the same by people in relative motion.  Another is that you can never get closer to a beam of light going away from you (i.e. go faster than the speed of light).  If you could, you would measure the speed of light differently than someone else, and you would be special.  The basic idea behind relativity is that, with regard to the laws of physics, no one is special.  \n\nThe second unsatisfying answer is E=mc^2.  In order to go faster, you have to accelerate.  Acceleration takes energy, and an accelerating body has more mass than a body in a constant state of motion (increase E in that equation m has go up, because c is the constant speed of light).  It just so happens that the mass doesn't go up in proportion to the rate of acceleration, but in relationship to how close you are to the speed of light.  Everytime you halve the distance between your speed and the speed of light, your mass doubles, and the amount of effort needed to get that next bit of acceleration doubles.  Getting to the speed of light would require infinite energy.
474792
(m)\n\nThe speed of light in a vacuum is exactly 299,792,458 metres per second (or 1,079,252,848.8  km·h-1, which is approximately 186,282.397 miles per second, or 670,616,629.4 miles per hour). This value is denoted by the letter c, reputedly from the Latin celeritas, "speed", and also known as Einstein's constant. Note that this speed is a definition, not a measurement, since the fundamental SI unit of distance, the metre, has been defined since 1983 in terms of the speed of light—one metre is the distance light travels in a vacuum in 1/299,792,458 of a second. The speed of light through a transparent medium (that is, not in vacuum) is less than c; the ratio of c to this speed is called the refractive index of the medium.
1126926
Since photons are particles and waves they react to electromagnetic fields created by electrons and protons in the medium the photon travels through.\n\nThe measure of how a photon changes in particular mediums is called the refractive index:\nn = c/v\nc is the speed of light in vacuum\nv is the speed in the medium\nn is the refractive index\n\nThe highest refractive number I could find (which means v is much smaller than c) was for \nIodine Crystal .............. 3.34\nBTW - this is why things like diamonds sparkle\n\nEdit:\nSilicon    ....................... 4.24\n\nEdit:\nProblems with saying that a photon's speed was reduced to zero:\n1) Refractive index goes to infinity (not really a problem but still interesting)\n2) Usually means the photon was absorbed (it did not come out of the medium)\n3) Light is a particle/electromagnetic wave, a v of zero creates a standing wave which I thought was wasn't possible for electromagnetic waves\n4) If the photon is merely caught inside the medium bouncing back and forth then v isn't really zero...  Just another way of saying that the photon was absorbed.
936725
Photons are mass-less elementary particles.  There is a famous, and simple, experiment to prove this.  A small pinwheel in a vaccum sealed light blub which is balanced on a pin can be made to spin in proportion to the amount of light that falls on the vanes of the pinwheel.  The vanes are colored alternatively black and white.  The white vanes reflect photons and the black vanes absorb them, so the thing spins like crazy, proving that the photons have enough energy and speed (momentum) to impart motion on the pinwheel.\n\nPhotons are said to have no 'intrinsic mass' which means they don't have mass when 'at rest.'  Of course photons are never 'at rest' so there's something called 'relativistic mass' which accounts for mass-like properties of things traveling at high speed (like the speed of light, which photons travel at).
353005
No. But, from the POV of the photon, they are everywhere along the path of the photon at once. See the answer on "lorentz contraction", because it's right, but I just wanted to clarify that photons are not, in fact, *everywhere* at once.\n\nOh, and from the POV of any subluminous velocity, no, they propagate at the speed of light, naturally.
1074848
Photon is not a substance.  It is pure energy.\n\nLight travels in discrete quantities called photons.  It is only called a particle due to the wave-particle duality.  That is, all energy and matter come in discrete amount, and travel in a wave (wave movement is not noticeable in matter because the wavelengths are extremely long)