Question

Infrared radiation are detected by:
A. Spectrometer
B. Pyrometer
C. Nanometer
D. Photometer

Answer 1

Hint: Infrared radiations are radiations above visible wavelength. Thermal radiation is usually under infrared region.

Complete step by step answer:
The infrared region which has a wavelength range from $0.75\text{ }\!\!\mu\!\!\text{ m to 1000 }\!\!\mu\!\!\text{ m}$. Infrared radiations are usually called heat radiations since thermal radiations fall under the infrared category. So out of the options given, a pyrometer is a device that works in the infrared region, it is used to measure the temperature of a body without being in contact with the body. But it cannot measure the whole infrared spectrum. The photometer is a device which can measure electromagnetic radiations from infrared to ultraviolet. So a photometer can be used to measure the whole infrared spectrum.
So the answer to the question is option (D)-Photometer.

Additional Information:
Most of the radiations emitted by objects in room temperature is infrared.
Infrared radiation behaves both as a wave and a particle in the form of photons.
Infrared radiation is extensively used in the fields of science, medicine, military and many more.
Spectrometers are used to study the spectrum of radiating bodies. If the body produces mixed spectrum a spectrometer is used to get a clear idea of the radiation.

Note: Most photometers make use of photodetectors, photoresistors or photomultipliers.
Modern DSLR cameras have photometers built in, in order to get correct exposure to a picture.
Spectrophotometry (which is the quantitative method to measure the reflection or transmission properties of a material as a function of wavelength) in infrared light is mainly used to study structure of substances, as given groups give absorption at defined wavelengths.