Excerpt from wikipedia: "EM waves carry energy, momentum and angular momentum away from their source particle and can impart those quantities to matter with which they interact."
Since EM waves are light waves, and photons doesn't have mass, how can EM waves carry momentum?
The building units of the electromagnetic radiation is the photons. The photons are a bunch of waves confined in space and have quantized energy. The energy in a photon is proportional to its frequency and equals hf where h is the Planck constant.
by observing the behavior of photons. it is found that in addition of energy it has momentum and consequently it has an effective mass or associated mass m. However the rest mass is zero because electromagnetic waves do not exist at rest. According to conservation of energy and mass, the energy has an equivalent mass according to the Einstein The energy E =m C^2= hC/ Lambda.. Then the momentum of the photon is equals mC.
The experiments which demonstrate the particle duality of the photons is the photo electric effect where the photons collide with electrons which are tiny masses and knock them out of the material. In high energy electromagnetic radiation the momentum is relatively large and observable.
Electromagnetic radiation behaves as waves in the transmission and as photons in interacting with the material.
Best wishes
The building units of the electromagnetic radiation is the photons. The photons are a bunch of waves confined in space and have quantized energy. The energy in a photon is proportional to its frequency and equals hf where h is the Planck constant.
by observing the behavior of photons. it is found that in addition of energy it has momentum and consequently it has an effective mass or associated mass m. However the rest mass is zero because electromagnetic waves do not exist at rest. According to conservation of energy and mass, the energy has an equivalent mass according to the Einstein The energy E =m C^2= hC/ Lambda.. Then the momentum of the photon is equals mC.
The experiments which demonstrate the particle duality of the photons is the photo electric effect where the photons collide with electrons which are tiny masses and knock them out of the material. In high energy electromagnetic radiation the momentum is relatively large and observable.
Electromagnetic radiation behaves as waves in the transmission and as photons in interacting with the material.
Best wishes
As explained by Prof. Zekry, the photon has effective mass. This is explain how light carry momentum.
Dear Suhas,
your question touches an important feature of the physical laws, namely the result of any observation changes if we modify the scale paraters.
If you observe something during different time duration or with different spatial resolution or with smaller or larger instrument then the numerical result of the observation changes. It is the renormalization group method which handles this isssue. Such a change is due to the interaction of the observed system and its environment. As a result, the mass, charge, or any other quantity which is used to characterize a free particle changes and looses its unique definition when the particle is allowed to interact with its environment.
The EM field, more precisely its elementary excitation, is massless in the absence of interaction with charges. Howevere in the latter case the phton mass becomes ill defined and all we have is a mass parameter which may or may not vanish, depending on the environment. For instance, the EM field behaves in a waveguide as it had a nonvanishing (effective)mass.
Under the "momentum of a photon" we understand the relativistic momentum, which is not a product of the rest mass and velocity. Its magnitude is given by E/c, where E is the energy and c is the speed of light.
It's a good question. Kuhn (Structure of Scientific Revolutions) argued that Newtonian mass and Relativistic mass (E=mc2) are NOT the same TYPE of 'thing'. A common way of talking about this is to say that the 'mass' in E=mc2 is really pointing to a 'mass-like' property or phenomenon. There are no Newtonian (localized) mass particles in Maxwell's Equations. Special Relativity – based on Maxwellian framework – has no gravitating masses. Einstein's efforts to link Maxwellian 'energy' (photons) with Newtonian 'mass' (vi. photo-electric effect) were only semi-successful – leading to the paradoxes of quantum theory). That led to Einstein to suggest General Relativity. There are a number of confirmations of relativistic effects associated with gravity. Einstein's mass-gravity is no longer a force, it's a geometry. This divorces it from any of the standard interpretations of 'energy'. The observations suggesting 'dark matter' are counter-evidence to both the Newtonian and Einsteinian theories of gravitational mass. The Higgs postulate is supposed to take care of the other 'missing mass' in Special Relativity – inertia. Curiously gravitational mass and inertial mass are defined and observed differently – yet measured locally to be the same to many decimal places. ––
Look for the source of acceleration.
Brian Greene's treatment of Newton's Bucket in his Fabric of the Cosmos is worth reviewing. Ignore the subsequent nonsense about String Theory (Emperor's New Clothes).
My book: Give Space My Love: An Intellectual Odyssey with Dr. Stephen Hawking
It offers a different approach to understanding these questions/problems and points toward a More General Theory.
The photon in a waveguide acquires a longitudinal polarization, because the boundary conditions break translation invariance explicitly. A mass, however, can't be defined, since Lorentz invariance is explicitly broken and only translations along the axis of the waveguide, at most, survive: each mode has a different mass and any superposition of modes doesn't have a well-defined mass at all. Interactions, in four spacetime dimensions, under conditions that respect Lorentz invariance, do not lead to a non-zero Lorentz invariant mass for the photon, absent spontaneous breaking of gauge invariance, which can occur in interactions with scalars, but not with fermions, only, but to a modification of the scaling dimension of the gauge field. That the photon remains massless in the presence of interactions with other fields is a consequence of gauge invariance, that's expressed by the Ward-Takahashi identities.
Yes, photons have mass. However, if a photon stopped moving, its masses vanishes and the evaporated mass turns into energy absorbed by the body that halted the photon.
Please read http://arxiv.org/pdf/1001.0029v2.pdf, especially the very end and , also version 1 of this paper on arxiv org. Read about contributions of Rainich to the topic of electromagnetic mass and gravity
Within Maxwell electromagnetic theory there exists two solutions ( in vacuum) transverse and longitudinal. For longitudinal solution one gets non-zero rest mass but it raises problem with gauge invariace and considered s unphysical..So photon with zero rest mass is the viable solution. The experimental observations also support it. You can look inot the following book for details : Bo Lehnert and Sisir Roy; Extended Electromagnetic Theory (World Scientific)
i think if we have a free photon it hasnt mass....but if we see photon on Intermediate particle in element particle ..it has mass and it is virtual photon....
A photon has no mass but has momentum, in the same way that the Kronecker delta function has no width but unit area. Because it has momentum it can transfer momentum to objects with mass if it changes direction or is absorbed.
The photon could behave as a massive object inside waveguides where a longitudinal component arises. Wang showed this case https://arxiv.org/ftp/arxiv/papers/0708/0708.3519.pdf and I also showed that it is possible in transmission lines where m=h R/c^2 L at Article Quantum Telegraph equation: New matter wave equation
It does not behave as a massive object in waveguide - it behaves as an object with momentum - just as it does when it hits a solar sail.
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