Physics Help Forum analogy between light intensity and gravity

 Light and Optics Light and Optics Physics Help Forum

 Nov 4th 2013, 06:35 AM #1 Junior Member   Join Date: Nov 2013 Posts: 4 analogy between light intensity and gravity It may be that I am not very smart or that I do not know the basic physics (most likely) but I wonder if the analogy between the law of gravitational attraction of a material point (as well as the electrostatic interaction) and, for example, the law of the light intensity of a point light source obey the same function (1 / r ^ 2) is or is not a coincidence. can anyone help me? thanks
 Nov 4th 2013, 08:11 AM #2 Physics Team     Join Date: Jun 2010 Location: Morristown, NJ USA Posts: 2,347 You are correct that both electromagnetic radiation (light) and gravity follow an invese square law (i.e. 1/r^2). Both effects are driven by the flux of massless force-carrying particles - photons for EM and gavitons for gravity - and the flux density of these particles (number of particles passing through a unit area per second) decreases as you get further from the source, per 1/r^2. So it's not really a coincidence, but rather a consequence of geometry.
 Nov 7th 2013, 08:18 AM #3 Junior Member   Join Date: Nov 2013 Posts: 4 this is very interesting. It is clear in the case of mass point (gravitons) and a point light (photons) but in the case where the source is a static electric point charge ? thank you very much
Nov 7th 2013, 08:38 AM   #4
Physics Team

Join Date: Jun 2010
Location: Morristown, NJ USA
Posts: 2,347
 Originally Posted by jjorg this is very interesting. It is clear in the case of mass point (gravitons) and a point light (photons) but in the case where the source is a static electric point charge ? thank you very much
The force carrier particle that is responsible for electromagnetic forces (such as attraction between oppositely charged particles per Coloumb's Law or the magnetic attraction between magnets of opposite poles) is actually the photon. Remember that electricity and magnetism are related to each other and together make up electro-magnetic radiation (light). So yes - since electromagnetic forces are conveyed by photons they obey the same inverse square law as light.

 Tags analogy, gravity, intensity, light

 Thread Tools Display Modes Linear Mode

 Similar Physics Forum Discussions Thread Thread Starter Forum Replies Last Post kiwiheretic Light and Optics 8 Nov 19th 2018 01:58 AM ling233 Quantum Physics 1 Oct 4th 2014 07:18 AM pramoda Waves and Sound 1 Mar 26th 2012 10:55 AM Steve George Waves and Sound 1 Nov 30th 2010 08:51 PM tanaki Waves and Sound 3 Nov 22nd 2009 04:21 AM