Answer : To provide heat.
Explanation :
Infrared waves are the waves having wavelength 700 nm to 1 mm.
The most common use of infrared waves is "to provide heat" i.e. in heat-sensitive thermal imaging cameras. It is a invisible wave. It can only sensed by a sensation of warmth.
For example :
When an object is hot, It will emit energy in the form of infrared waves.
So, correct option is (b)
