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Why laser light is mono chromatic

  1. Mar 3, 2005 #1
    Hello.,
    how r u guys .i want to ask a question from u people.
    Question seem very easy but i want detailed answer of the question.


    Question is " WHY LASER LIGHT IS MONO CHROMATIC"?
    " WHY META STABLE SATES hAVE GREATER LIFE TIME'




    i will be very thankful to u people.

    waiting for ur urgent reply
     
  2. jcsd
  3. Mar 4, 2005 #2
    Any body genius plz help me
     
  4. Mar 4, 2005 #3
    I don't know how much you know about the subject already so I will try to keep it simple.

    Photons that are given off in a laser are caused by electrons going from a high energy level to a lower energy level. The photons that are given off have a wavelength determined by the amount of energy given off by the electron as it drops to a lower level.

    Laser light can be monochromatic because the electrons can't exist in what is known as the "band gap". If an electron is to be excited to a higher energy level it has to overcome the band gap energy. When it drops back down it drops by the same amount of energy. So each electron that goes from high to low energy level gives off a photon with the same energy. Since all the photons have the same energy they are all the same wavelength.

    This is a simplification, but if it's an intro course you need this for it should be good enough.
     
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