LIGHT AND RADIATION TRANSDUCERS The spectrum of electromagnetic radiation extends from radio waves(less than 1 Hz) to gamma rays(1020 Hz or higher). The very low frequency radio waves have the longest the gamma rays the shortesy In between these extremes a all wavelengths; the other categories of electromagnetic radiation, including light(see Fig. 14.30). For our purposes of classification, light will be defined to include the radiations belonging to the infrared, visible light, and ultraviolet rtions of the electromagnetic spectrum. section we are interested primarily in those light radiation and convert it into an electrical form.The general class of light-radiation transducers, also known as phototransducers, is used to detect the presence and inten sity of light under various circumstances. In fact, many photo-transducers can be made Jmuch more sensitive to light radiation than the human eye is The three primary types of light-to-electrical energy transducers are 1. Photoemissive devices 2. Photoconductive devices 3. Photovoltaic devices Each of these types possesses special advantages over the others.