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Thread: Confused about E!

  1. #1 Confused about E! 
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    So, let's say we are talking about a photon. We can find E by the equation E=pc, which only works for light. But, when I take p=h/λ, then I fill in λ with v_p/f since λ=v_p/f, so then we get p=hf/v_p, then since E=hf we get p=E/v_p, then to p(v_p)=E, and E=pc for light so we get E=pc=p(v_p), which implies c=v_p, which in a vacuum is true for light but quite frequently isn't. I am confused! What am I doing wrong!
    v_p is phase velocity


    Last edited by Muon321; March 12th, 2013 at 08:37 PM.
     

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  3. #2  
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    Quote Originally Posted by Muon321 View Post
    So, let's say we are talking about a photon. We can find E by the equation E=pc, which only works for light. But, when I take p=h/λ, then I fill in λ with v_p/f since λ=v_p/f, so then we get p=hf/v_p, then since E=hf we get p=E/v_p, then to p(v_p)=E, and E=pc for light so we get E=pc=p(v_p), which implies c=v_p, which in a vacuum is true for light but quite frequently isn't. I am confused! What am I doing wrong!
    v_p is phase velocity
    You have already opened two identical threads here and your question has been answered. Why do you feel compelled to spam multiple forums with the same nonsense?


     

  4. #3  
    Ophiolater Nehushtan's Avatar
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    And here.
    Holding on to anger is like drinking poison and expecting the other person to die.
     

  5. #4  
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    Muon321. If you are still confused about this topic, having provoked discussion elsewhere and received advice and what looks like satisfactory answers to me, you need to restate - in a new thread - exactly where your confusion now lies.

    This thread is closed.
    "Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill
    "nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke
     

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