1. The problem statement, all variables and given/known data In an experiment to measure photon statistics of thermal light, the radiation from a black-body source is filtered with an interference filter of bandwidth 0.1 nm centered at 500 nm, and allowed to fall on a photon-counting detector. Calculate the number of modes incident on the detector, and hence discuss the type of statistics that would be expected. 2. Relevant equations 3. The attempt at a solution I feel pretty lost with this question. I'm not even sure what is meant by MODES. Is it the different frequencies of the photons in the 499.05 to 500.05 nm range?