Infrared Waves Definition. The infrared radiation or waves can be defined as waves with the wavelength in the range of 0.75 Âµm to 1 mm in the EM spectrum. Electromagnetic waves ranges from the very high wavelength (kms) to low wavelength (picometers).he infrared waves are of wavelength well below the visible region of the EM spectrum. The infrared are not visible to our eye since they are outside the narrow window of the visible frequencies. In other words, we can say that we are blind for all the spectrum except the visible spectrum.