How do the terms photocell and thermocouple hold clues that show the type of energy taken in by each device?

The term "photocell" suggests that the device is sensitive to light energy, as it typically refers to a sensor that detects light levels and converts them into electrical signals. In contrast, "thermocouple" indicates that it measures temperature differences, converting thermal energy into electrical voltage. Thus, the names highlight that photocells interact with light energy while thermocouples are focused on thermal energy.