Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Energy Fluxes of Two Objects

  1. Feb 8, 2012 #1
    1. The problem statement, all variables and given/known data
    Suppose two objects have energy fluxes, f and f + Δf, where
    Δf ≪ f. Derive an approximate expression for the magnitude difference
    Δm between these objects. Your expression should have Δm
    proportional to Δf.


    2. Relevant equations
    Δm = m2 - m1 = 2.5 * log(f1/f2)


    3. The attempt at a solution
    So the issue is that I'm not sure which of these solutions would be the better one to work with. However, I did make an approximation with the one as shown below and I'm not sure if it is quite accurate enough. Any assistance is greatly appreciated.

    Attempt 1: Δm = 2.5 * log(f / f+Δf) = 2.5 * [ log(f) - log (f + Δf)]

    or,

    Attempt 2: Δm = 2.5 * log(f+Δf / f) = 2.5 * log(1 + Δf/f) ≈ 2.5*Δf

    The second attempt seems more correct to me but I would feel more confident with a second opinion.
     
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted