I was trying to measure the photo responce of my thin film the photoresponce is showing sinosoidal behaviour . Is it some characteristic or error ? Need some analytic remarks from the experts .
The first step to identify the phenomenon would be to identify the frequency. What is the time unit?
Samples that spontaneously have oscillatory comportments are rare... 50 to 60hz pollution is of course classic but other sources are possible. More details on the experiment (sample and apparatus) are necessary to identify the source of the problem.