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Homework Help: Fundamental Particles - Meson Decay Question

  1. May 15, 2012 #1
    1. The problem statement, all variables and given/known data
    The pion-zero meson has its mass quoted as 135.0MeV/c2.
    It decays into two gamma rays:
    0 → γ + γ
    b) Assuming the ∏0meson to be initially at rest, calculate the energy and hence the wavelength of the two gamma rays.

    2. Relevant equations
    E= hc/λ

    3. The attempt at a solution
    Part a) just wanted me to calculate the mass in kg; which was fine, but I'm having trouble with part b).
    E = 135.0 MeV, which I get to be 2.16x10-11J
    I halved this value as there are two gamma rays, to get 1.08x10-11J
    Using this value for E in the equation E=hc/λ, my value for λ is 1.84x10-14; however according to my book the answer should be 1.98x10-14
    Could someone please tell me where I'm going wrong?
    Thank you :smile:
  2. jcsd
  3. May 15, 2012 #2


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    Homework Helper
    Gold Member

    Hello Magda|A380,

    Welcome to Physics Forums!
    For what it's worth, I calculated the same answer that you did (λ = 1.84 x 10-14 m, to three significant figures).
  4. May 16, 2012 #3
    Thanks collinsmark :)
    Yeah, my books is known to be wrong sometimes and 1.84 x 10-14 m still lies within the gamma ray wavelength range; so I'll accept it as the correct answer.
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