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'''Photons''' ('''γ<math>\gamma</math>''') are [[boson]]s responsible for mediating the [[Electromagnetic Interaction|electromagnetic interaction]] and are the [[Subatomic Particle|particle]] associated with [[Electromagnetic Wave|electromagnetic waves]].

: The '''photon''' is denoted with the lower case Greek letter γ <math>\gamma</math> (gamma).: '''Photons''' carry [[energy]] from one place to another.: '''Photons''' have no [[mass]] or [[Electrical Charge|charge]] ===About Virtual Photons===: '''Virtual photons''' a [[model]] for the mechanism of action of the [[Electromagnetic Interaction|electromagnetic interaction]], but they are not strictly 'real'.: '''Virtual photons''' have no [[mass]] and therefore can mediate the [[Electromagnetic Interaction|electromagnetic interaction]] over an infinite range.: '''PhotonsVirtual photons''' carry [[momentum]] without carrying [[mass]] and are therefore able to change the direction of motion of other [[Subatomic Particle|subatomic particles]].: '''PhotonsVirtual photons''' do not carry [[Electrical Charge|charge]], but allow [[Subatomic Particle|particles]] with [[Electrical Charge|charge]] to exchange [[momentum]]. ===Equations=======Momentum of a Photon==== <math>p = \frac{h}{\lambda}</math> Where  <math>p =</math> The [[momentum]] of the '''photon'''. <math>h = </math> [[Planck's Constant]] (<math>6.63\times10^{-34}Js</math>). <math>\lambda =</math> The [[wavelength]] of the [[Electromagnetic Wave|wave]] associated with the '''photon'''. ====Energy of a Photon==== <math>E = hf</math> Where <math>E =</math> The [[energy]] of the '''photon'''. <math>h = </math> [[Planck's Constant]] (<math>6.63\times10^{-34}Js</math>). <math>f =</math> The [[frequency]] of the [[Electromagnetic Wave|wave]] associated with the '''photon'''. ====The Speed of Light==== <math>c = f\lambda</math> Where <math>c =</math> The speed of [[light]] (<math>3.00\times10^{8}ms^{-1}</math> in a [[vacuum]]). <math>\lambda =</math> The [[wavelength]] of the [[Electromagnetic Wave|wave]] associated with the '''photon'''. <math>f =</math> The [[frequency]] of the [[Electromagnetic Wave|wave]] associated with the '''photon'''. ===Examples==={| class="wikitable"|+The '''virtual photon''' is shown mediating the [[Electromagnetic Interaction|electromagnetic interaction]].|[[File:FeynmanDiagramProtonProton.png|center|300px]]|[[File:FeynmanDiagramElectronElectron.png|center|300px]]|-| style="height:20px; width:300px; text-align:center;" |This [[Feynman Diagram]] shows the [[Electromagnetic Interaction|electromagnetic interaction]] between two [[proton]]s exchanging [[momentum]] via the '''virtual photon'''.| style="height:20px; width:300px; text-align:center;" |This [[Feynman Diagram]] shows the [[Electromagnetic Interaction|electromagnetic interaction]] between two [[electron]]s exchanging [[momentum]] via the '''virtual photon'''.|} ===References=======AQA==== :[https://www.amazon.co.uk/gp/product/019835939X/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=019835939X&linkCode=as2&tag=nrjc-21&linkId=57e96876985fc39b1a3d8a3e3dc238b6 ''Photons, page 95, GCSE Physics; Third Edition, Oxford University Press, AQA ''] ====OCR====:[https://www.amazon.co.uk/gp/product/0198359837/ref=as_li_tl?ie=UTF8&camp=1634&creative=6738&creativeASIN=0198359837&linkCode=as2&tag=nrjc-21&linkId=3c4229e8b023b2b60768e7ea2307cc6f ''Photons, pages 178-179, Gateway GCSE Physics, Oxford, OCR '']