1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Presumed mass content of photon as gravitational source

  1. Feb 10, 2016 #1

    I have read some of the posts which discuss the meaning and mistakes involving the equation:
    ## m_0 = \frac{h f }{c^2}.##

    My question has to do with gravitation. I would like to know if it is correct to associate to a photon with frequency f, crossing a region near a mass M, a gravitational influence based on the "photon's mass content" above described (even if the concept of rest mass is not applicable).

    Best wishes,

  2. jcsd
  3. Feb 10, 2016 #2


    User Avatar
    2017 Award

    Staff: Mentor

    That doesn't work. The effect is more similar to an object with twice the mass, but you still have non-negligible effects from the fast motion that doesn't allow to apply Newton's formula for example.
  4. Feb 10, 2016 #3
    But near the surface of the earth, for example, being a region where we can approximate de gravitational force on a mass m to mg, and which implies that all bodies will fall with the same acceleration g, the photon will also behave like this, isn´t it?
    I recall an interesting exercise proposed by Paul Hewitt in Physics Teacher magazine, in which he asks for a comparison between the fall of a ball and a beam of laser light, both bouncing back and forth in perfectly reflecive walls.
    ball and light drop hewitt.jpg
  5. Feb 12, 2016 #4
    Just for the sake of good references, in the previous post (#3) I attached an illustration by Paul Hewitt, relative to the very problem I cited.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook