1. A method for detecting whether an object of interest is being carried by a subject, the method comprising: coarsely scanning the subject with an electromagnetic radiation using a plurality of frequencies of electromagnetic radiation generated by at least one of spectral tuning of a narrow band source and using multiple discrete frequency sources, wherein the frequencies are selected based upon a known spectroscopic signature of the object of interest; measuring reflective intensity of radiation reflected from the subject; and, without generating an image, detecting the presence or absence of the object of interest based upon the presence or absence of the known spectroscopic signature of the object of interest from the measured reflective intensity.