In this chapter, the principles of electro-magnetic radiation are described in sections 1.2-1.4, the types of remote sensing with respect to the spectral range of the eletro-magnetic, radiation in section 1.5, the definition of radiometry in section 1.6, black body radiation in section 1.7, electro-magnetic characteristics in sections 1.8 and 1.9, solar radiation in section 1.10 and atmospheric behavior in sections 1.11 and 1.12.