Which of the following devices can be used to detect radiant heat ?
A
Liquid thermometer
B
Six's maximum and minimum thermometer
C
Constant volume air thermometer
D
Thermopile
Correct Answer: Thermopile
Based on the thermoelectric effect, the thermopile can be used as a heat sensor to measure thermal radiation. A thermopile is made of thermocouple junction pairs connected electrically in series. Thermocouples near the ground measures radiant energy.