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Do you fancy argon-ion lasers?

  1. Nov 29, 2009 #1
    Do you fancy argon-ion lasers??

    I sure dont. =/

    1. The problem statement, all variables and given/known data
    I dont. This is a practice test problem and I cannot figure it out. Frustrating!

    An argon-ion laser emits a blue-green beam of light with a wavelength of 488 nm in a vacuum. What is the difference in energy in joules between the two energy states for the atomic transition that produces this light?

    6.18 × 10–20 J

    1.05 × 10–20 J

    5.10 × 10–28 J

    4.08 × 10–19 J

    4.76 × 10–24 J

    2. Relevant equations

    See below. Im not sure its right though since im not producing one of the multiple choice questions.

    3. The attempt at a solution

    This is what I came up with so far:
    so we know the wavelength (l) of the light emitted.

    now, E (energy) is h * n (h = Plancks constant, n = frequency)


    E = h * n

    but also, l = c T = c / n (T is the period of the oscillation of the emitted light) which means

    n = c / l


    E = h * c / l

    with this formula E can be computed

    (c = 3 * 10^8 m/s is the speed of light)
    my answer isnt any of the above, however. :(

    help? =)
  2. jcsd
  3. Nov 30, 2009 #2


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    Homework Helper

    Re: Do you fancy argon-ion lasers??

    Try again. The formula E=hc/l is right, and if you plug in the right numbers, it DOES give you one of the answer choices.
  4. Nov 30, 2009 #3
    Re: Do you fancy argon-ion lasers??

    I keep getting 4.07 x 10^-28

    Thats a combination of c and d haha. :(
  5. Nov 30, 2009 #4
    Re: Do you fancy argon-ion lasers??

    Update(since I know you're all eager to hear about my adventures):

    I got it!! I just had to convert nm to m haha. Duh.

    Oh, and I got 100% on my quiz today!!WOOT WOOT!!!

    Id start breakdancing right now out of pure joy, but I dont wanna snap my legs.

    This means Ill get an A for 2nd semester physics. I got an A in 1st semester too and I dont even like the subject.

    *llama dance*
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