Basic Tranducers for Radiation
M. J. Usher · 1985
The term photodetectors is usually applied to transducers for a very narrow range — the visible and near infra-red — of the electromagnetic spectrum. There is of course no real limit to the electromagnetic spectrum; it stretches from very low frequency waves of less than 1 Hz, observed by magnetometers, to X-rays and γ-rays of frequencies up to 10 20 Hz, as indicated in figure 7.1. However, we will confine our attention here to photodetectors, since this range is particularly important in many types of measurement.