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Light Intensity

  1. Jun 9, 2009 #1

    J89

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    1. The problem statement, all variables and given/known data
    A 60-cd lamp and a lamp of unknown intensity are placed 3m apart. A light meter is moved between the two lamps until it reads the same illuminance from both lamps. The light meter is then 1.5 m away from the 60-cd lamp. What is the intensity of the other lamp?


    2. Relevant equations
    E=P/d^2



    3. The attempt at a solution
    No clue
     
  2. jcsd
  3. Jun 10, 2009 #2

    rl.bhat

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    Homework Helper

    Use E = P1/d1^2 = P2/d2^2.
    The point is whether the light meter is between the two lamps or outside the two lamps?
     
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