1. Remote Sensing Remote sensing includes techniques to derive information from a site at a known distance from the sensor.1 Remote sensing is the science and art of obtaining information about an object, area, or phenomenon through the analysis of data acquired by a device that is not in contact with the object, area, or phenomenon under investigation.2
Introduction to Remote Sensing system: data acquisition and processing, Applications, Multi concept in remote sensing.

2. Electromagnetic Radiation
Fig: The regions of the Electromagnetic Spectrum: wavelength(λ) is inversely proportional to frequency (ν). In the visible, the rainbow colours starting from the shorter λ are violet, blue,cyan, green and yellow,orangeandred

3. Fig: The electromagnetic spectrum, illustrating the wavelengths and names of various types of radiation

4. Concept of Electromagnetic spectrum:
Electromagnetic (EM) spectrum is mono-dimensional continuous,consisting of a set of radiations ordered according to wavelength, frequency or photonic energy; it includes waves of any wavelength, ranging from fractions of Angstrom (one tenth of a millimicron Å=10−10m) to many kilometres.
For practical use, the electromagnetic spectrum is divided into regions, according to wavelength (Fig. 4.2 and Table 4.1):visible light, so defined as its range is within the interval of the human eye’s spectral sensibility; cosmic rays, gamma (γ), X-rays, ultraviolet, infrared, visible, microwaves, radio waves – these are the most well known energy types existing in nature. EM energy as waves propagating in a vacuum in harmonic motion, i.e. by regular intervals in time, and at light speed .

5. wavelength(λ): measured in microns (μm), is the distance from one peak, orcrest, of a wave of energy to the next corresponding peak or crest;
frequency (ν): is the measure of the number of occurrences of repeating EM
waves per unit of time. This is described as the number of waves made per second, measured in cycles per second or hertz (Hz).

6. Stefan–Boltzmann Law
This law mathematically expresses the rate of radiation emitted per unit area:
This furnishes the total quantity of energy emitted by a surface calculated on the whole electromagnetic spectrum, for any temperature
E=σT4

7. Wien’s displacement law: points out the wavelength value in correspondence with
the maximum electromagnetic emission at a defined temperature.
The relationship between the temperature (T) of a radiating body and its
wavelength of maximum emission (λmax): λmax= C/T