1. Not finding help here? Sign up for a free 30min 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!

Uncertainty Principle Problem

  1. May 31, 2012 #1
    I'm given a form of Heisenberg's uncertainty principle in the form of:

    [tex]\Delta E\Delta t\geq h[/tex]

    I need to determine a time interval which would allow a laser to cover the whole visible spectrum, from 400 to 700nm.

    Now given the relationship is on on a relative scale I used the approximation:
    [tex]\Delta E\Delta t\approx h[/tex]

    I then used the following formula:

    [tex]E=\frac{hc}{\lambda}[/tex]
    and differentiated like so:
    [tex]\Delta E = -\frac{hc}{\lambda ^{2}}\Delta \lambda[/tex]
    Which I then substituted back in:

    [tex](-\frac{hc}{\lambda ^{2}}\Delta \lambda)\Delta t \approx h[/tex]

    Is this correct so far?
     
  2. jcsd
  3. May 31, 2012 #2
    Actually, the equation is not correct (I'm assuming h to be the planck's constant). It would be:

    $$ \delta E\mbox{ }\delta t\geq\frac{\hbar}{2}=\frac{h}{4\pi} $$

    Also, I don't see what you differentiated with respect to.
     
  4. May 31, 2012 #3
    I see the issue. The problem set gave us the wrong h...I'll re run it and let you know the result.

    EDIT: I'm confused now. Should I be using h bar in all of the locations? This error in the problem set has mixed me up.
     
    Last edited: May 31, 2012
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Uncertainty Principle Problem
  1. Uncertainty Principle (Replies: 12)

Loading...