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Quantum energy levels

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  1. Apr 20, 2015 #1
    1. The problem statement, all variables and given/known data
    A 0.39 kg mass falls from a height of 2.9 m. If all of the energy of this mass could be converted to visible light of wavelength 5.5 × 10^−7 m, how many photons would be produced? The acceleration of gravity is 9.8 m/s^2 . Planck’s constant is 6.63 × 10^−34 J · s, and the speed of light is 3 × 10^8 m/s.

    2. Relevant equations
    E=hc/λ
    p=h/λ
    x=.5at^2

    3. The attempt at a solution
    E=hc/λ=(1.99x10^-25)/(5.5x10^-7)=3.618x10^-10J
    x=.5at^2 > 2.9=.5(9.8)t^2 > t=.769s
     
  2. jcsd
  3. Apr 20, 2015 #2
    Well, I think you can just calculate the initial energy E=mgh, assuming it was at rest before the fall.
    You already have the energy of one photon Ephoton=hc/λ, so the number of photons will be just E/Ephoton
     
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