Electromagnetic radiation

Remote sensing starts with electromagnetic radiation. Light is a particular type of electromagnetic radiation that can be sensed by the human eye, but this energy exists at a very wide range of wavelengths. For measuring electromagnetic wavelengths, we use a basic unit called ‘micron’. We divide the spectrum of waves into sections according to the wavelength. The shortest waves are called gamma rays. They have a very high frequency, and wavelengths of 10e^-6 microns or less. The longest waves are called radio waves. They have a very low frequency, and wavelengths of many kilometres.