Ems interaction with the atmosphere
- 1. EMR INTERACTION WITH THE ATMOSPHERE The most important source of electromagnetic radiation is the sun. Before sun’s energy reaches the surface of the earth three fundamental interaction in the atmosphere are possible . These are absorption, transmission , and scattering . 1. Absorption: Electromagnetic energy travelling through the atmosphere is partly absorbed by various molecules. The most efficient absorbers of solar radiation in the atmosphere are ozone(O3),water vapour (H2O),and carbon dioxide (CO2) Ozone serves to absorb the most harmful (to most living things) ultraviolet radiation from the sun.
- 2. 2. TRANSMISSION Some energy are transmitted through the atmosphere in the wave length from 0 to 22 µm which is called “atmospheric windows” Without this “atmospheric windows” remote sensing process is not possible .
- 3. 3. SCATTERING Scattering are occurs when particles or large gases molecules are present in the atmosphere. Due to the interaction electromagnetic radiation is redirected from its original path. How much scattering are takes place depends on several factors including the wave length of the radiation, the abundance of particles or gases, and the distance the radiation travels through the atmosphere .there are three types of scattering which take place :– Rayleigh scattering, Mie scattering, and Non selective scattering .
- 4. RAYLEIGH SCATTERING This scattering occurs when particles size are very small compared to the wavelength of the radiation . These could be particles such as small specks of dust or N2 and O2 molecules . Rayleigh scattering is the dominant scattering mechanism in the upper atmosphere. Sky appears blue in colour due to this kind of scattering .
- 5. MIE SCATTERING Mie scattering occurs when the particles are just about the same size as the wavelength of the radiation. Dust, Pollen , smoke, water vapour are the common causes of mie scattering which tends to affect longer wavelength than rayleigh scattering . This type of scattering occurs mostly in the lower portions of the atmosphere where larger particles are abundant.
- 6. NON-SELECTIVE SCATTERING The final scattering is non selective scattering , occurs when the particles are much larger than the wavelength of the radiation . Water droplets and large dust particles can cause this type of scattering . Non selective gets its name from the fact that all wavelength are scattered about equally. This type of scattering causes fog and clouds to appear to our eyes because blue , green, and red light are scattered in approximately equal quantities (Blue + Green + Red = white light )