Suppose you are inside a black body radiation cavity which is at temperature T. Your job is to measure the radiation field in the frequency interval from 1014 to 89 x1014 Hz. You have a detector to do the job. What should the temperature of the detector (T’) be?
Explain your answer.
Possible options are T’>T, T’=T, T’<T, T=0K, or is the temperature of the detector is irrelevant to the measurement?