EM Waves

Infra red radiation is detected by

  1. photometer
  2. nanometer
  3. spectrometer
  4. pyrometer


A photometer is an instrument that measures light intensity or optical properties. Nanometer is unit of length. Spectrometer is an apparatus used for recording and measuring spectra.

A pyrometer is a type of remote-sensing thermometer used to measure the temperature of a surface. Infrared radiation can be detected by pyrometer.

The correct option is D.