# Luminosity per unit frequency

jmm5872
I am just trying to understand exactly what luminosity per unit frequency is. I know that luminosity (L = 4PI(r2)(flux)) is amount of energy per unit time, but not sure what it means when it is also per unit frequency.

The question has a cosmic source of 100 solar luminosity, all emitted with the frequency of 22 GHz, and the object is 0.001 pc in radius.

Do I calculate the luminosity (100*Solar Luminosity), actually I don't even know how to begin. I guess I am just confused at what exactly luminosity per unit frequency is and how to get it.