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Homework Help: Find the power emitted (quantium mech)

  1. Oct 16, 2011 #1
    1. The problem statement, all variables and given/known data
    consider a blackbody at t=7000 what is the power emitted through a hole 1m between[itex]\lambda[/itex]= 4000 and 4001 angstrom

    2. Relevant equations

    P([itex]\lambda[/itex]) d[itex]\lambda[/itex]=A(2[itex]\pi[/itex]hc2/[itex]\lambda[/itex]5(......)d[itex]\lambda[/itex]

    3. The attempt at a solution
    my question is the math, I thought u had to make a integral on both sides and have it go from 4000 to 4001, but the solution does not do this. they just plug in 4000 for [itex]\lambda[/itex] and for d[itex]\lambda[/itex] they have 10-10 Is both ways correct? I dont remember what i got when i did the integral
  2. jcsd
  3. Oct 17, 2011 #2
    Strictly speaking, your way is "more correct". They use the fact that the range for lambda is very small and the expression is not going to change a lot. This way, the integration turns into a multiplication.
  4. Oct 17, 2011 #3
    ok thanks
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