a unit of detectivity, that is, the ability of an electronic device to detect radiant energy such as light waves or infrared radiation. In a 1959 paper, R. Clark Jones defined the "specific detectivity" of a device to be = [square root ( Aw)]/, where is the area of the detector, is the frequency bandwidth, and is the power of the noise generated by the device. The quantity is measured in the complex unit cm·Hz1/2/W, customarily called the "Jones." In modern equipment, detectivities are often quite large, in the range of 109 to 1012 Jones.