# Fourier transform physical meaning [closed]

What is the physical meaning of the Fourier transform expressed at the spectral density? Also, what is the relationship between the Fourier transform and the total energy of an oscillating system? What is the role of a Dirac delta function in the process of such an understanding?

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voted to migrate to physics.stackexchange.com –  joriki Nov 5 '12 at 7:57
Why is this off topic? –  ramanujan_dirac Jan 13 '13 at 5:13