sentences:  The formation behavior of condensation on the mirror's surface can be registered by either optical or visual means.In both cases, a light source is directed onto the mirror and changes in the reflection of this light due to the formation of condensation can be detected by a sensor or the human eye, respectively.The exact point at which condensation begins to occur is not discernible to the unaided eye, so modern manually operated instruments use a microscope to enhance the accuracy of measurements taken using this method.