How useful is the electromagnetic spectrum to remote sensing?

There's is no concept of active or passive Remote Sensing will be there if there are no Electro-Magnetic Spectrum( EMS ). First of all, Remote Sensing, Is the process of getting the information from a remote location, without being personally in that location. read more

The fundamental unit of electromagnetic phenomena is the photon, the smallest possible amount of electromagnetic energy of a particular wavelength. Photons, which are without mass, move at the speed of light—300,000 km/sec (186,000 miles/sec) in the form of waves analogous to the way waves propagate through the oceans. read more