Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Casimir Effect question

  1. Oct 27, 2012 #1
    Greetings!

    I would love to hear people's thoughts on the following:

    My (basic) understanding is that the Casimir Effect acts upon 2 closely spaced parallel conducting plates, because the photon pressure between the plates is less - only wavelengths which are multiples/divisors of the plate spacing can exist.

    If one of the plates was in fact a semiconductor, when it ceased to conduct would there be a net force on the (permanently) conducting plate towards the centre of the 2 plates? If the semiconductor were driven on/off at high frequency, could this force become substantial? ( e.g. a potential propulsion for spacecraft )

    I haven't been able to find mention of this particular theory on t'interweb - I'm sure there are countless flaws with the theory but I've been out of the physics game for too long now!

    thanks in advance
     
  2. jcsd
  3. Oct 27, 2012 #2
    The Casmir force would be determined by the conductivity of the semiconductor. The conductivity of the semiconductor would depend on how it was doped, the temperature of the semiconductor, whether it was illuminated, and other microscopic details. However, the Casmir effect wouldn't be sensitive to the microscopic details. The Casmir effect would only be affected by the macroscopic (i.e., average) conductivity.
     
  4. Oct 27, 2012 #3

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    Besides, what you are describing does not conserve momentum.
     
  5. Oct 27, 2012 #4
    OK, thanks - but wouldn't the momentum be taken from the external photons?
     
  6. Oct 27, 2012 #5

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    What external photons?
     
  7. Oct 28, 2012 #6
    The radiation pressure acting on the permanently conducting plate towards the midpoint - if there wasn't a matching force the other side of it, wouldn't momentum be transferred from the photons comprising the radiation into the momentum of the plate?
     
  8. Oct 28, 2012 #7

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    I don't think you are understanding this. It's not like there is a real bath of photons out there that can somehow be shielded if going from the left but not if going from the right.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Casimir Effect question
  1. Casimir effect (Replies: 1)

  2. Casimir Effect (Replies: 1)

  3. Casimir Effect (Replies: 5)

  4. The Casimir effect (Replies: 1)

Loading...