# Homework Help: J-space calculations

1. Jun 16, 2010

### Piano man

Hi,

I'm currently studying my Quantum Mechanics notes from college last year and I've got to the bit about j-space calculations. The slide is very scant on details and google isn't yielding anything on this either.
I would skip it but it seems important for deriving expressions such as Energy $$E(\lambda)d\lambda =k_b T\left[\frac{8\pi L^3}{\lambda ^4}\right]d\lambda$$ and the energy density in a cavity $$u(\omega)d\omega = \frac{\hbar\omega^3}{\pi^2c^3}\frac{1}{e^{\hbar\omega/k_bT}-1}d\omega$$

Does anyone have any good sources for learning more about j-space?

Thanks

2. Jun 16, 2010

### zzzoak

You may search the black body radiation for the second equation.