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\sect{Radiation from 1D balckbody fiber}

Given an optic fiber with length ${L}$ and it's section area is
${A}$. The fiber is in thermic equilibrium in temperature ${T}$.
Assume the fiber is a one dimensional medium for the electromagnetic
field (relate to the magnetic radiation as a photon gas).

\begin {itemize}

\item[(a)]
What is the condition (on temperature)so the one dimensional
proximity will be valid?

\item[(b)]
What is the electromagnetic energy density per length unit?

\item[(c)]
What is the radiation pressure on the fiber edges?

\item[(d)]
Assuming that the radiation can emit from the boundary of the fiber,
what is the emitting radiation flow (energy per time unit)?

\item[(e)]
What is the spectral distribution ${J\left(w\right)}$ of the
emitting radiation flow?

\item[(f)]
What is the entropy and what is the heat capacity of the system?

\end {itemize}

Given:
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\[\int_{0}^{\infty}\frac{x}{e^{x}-1}dx=\frac{\pi^{2}}{6}\]



