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!

Estimate the lifetime of the excited state that produced this line.

  1. May 15, 2012 #1
    1. The problem statement, all variables and given/known data

    An atomic spectrum contains a line with a wavelength centered at 460 nm. Careful measurements show the line is really spread out between 459 and 461 nm.

    Estimate the lifetime of the excited state that produced this line.

    2. Relevant equations

    Change in Frequency = Speed of light/Change in Wavelength

    Time = The inverse of frequency

    3. The attempt at a solution

    Change in wavelength = 461nm -459 nm = 2 nm or 2x10^-9 meters

    Change in frequency = speed of light/change in wavelength = (3x10^8)/(2x10^-9) = 1.5x10^17 in units of s^-1

    Life time = 1/(1.5x10^17) = 6.7*10^-18 seconds

    But this is wrong and I don't know where to go from here. Please help!
     
  2. jcsd
  3. May 15, 2012 #2

    vela

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Education Advisor

    Neither of your relevant equations is correct. For the first one, use ##\lambda_1 = c/f_1## and use ##\lambda_2 = c/f_2## and find what ##\lambda_1 - \lambda_2## equals. The second equation only applies if the time is the period of oscillation, which it isn't in this case.
     
    Last edited: May 15, 2012
  4. May 15, 2012 #3

    fluidistic

    User Avatar
    Gold Member

    I'd have had approached the problem differently but I might be totally wrong.
    Let me write the following to vela (please do not read this OP!):
    Hey vela :)
    I'd have used HUP for that one. So instead of looking for the delta lambda, I'd have looked for delta E and then apply the HUP to get delta t.
    What do you think about the approach?
     
  5. May 15, 2012 #4

    vela

    User Avatar
    Staff Emeritus
    Science Advisor
    Homework Helper
    Education Advisor

    Yeah, that's correct.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Estimate the lifetime of the excited state that produced this line.
  1. Excited state (Replies: 0)

  2. Excited state lifetime (Replies: 2)

Loading...