Infrared optical ______ can be used for measuring and monitoring temperatures and hot spots of jet engine rotor blades.

pyrometer

The correct answer is option 3. pyrometer.

Infrared optical pyrometer can be used for measuring and monitoring temperatures and hot spots of jet engine rotor blades.

A pyrometer is an instrument used for measuring high temperatures, especially in environments where direct contact is not feasible or safe. Infrared pyrometers operate by detecting the thermal radiation emitted by objects and converting it into a temperature reading. They are commonly used in industrial settings, such as in the monitoring of jet engine rotor blades, where precise temperature measurements are crucial for ensuring safe and efficient operation.