EMR And Its Interaction With Atmophere And Earth Material
1.What is Remote Sensing?
Remote sensing is the science and art of obtaining information about object, area, or phenomena through the analysis of data acquired by a device that is not in contact with the object, area, or phenomena under investigation.
2.What are all the applications of remote sensing?
In many respects, remote sensing can be thought of as a reading process. Using various sensors, we remotely collect data that may be analyzed to obtain information about the objects, areas,or phenomena beinginvestigated.
The remotely collected data can be of many forms, including Variations in force distributions, acoustic wave distributions, or electromagnetic energy distributions.
3.Write the physics of remote sensing ?
Visible light is only one of many forms of Electromagnetic energy. Radio waves, heat, ultraviolet rays, and X-rays are other familiar forms. All this energy is inherently similar and radiates in accordance with basic wave theory. This theory describes electromagnetic energy as traveling in harmonic, sinusoidal fashion at the 'velocity of light' c. The distance from one wave peak to the next is the wave length ?, and the number of peaks passing a fixed point in space per unit time is the wave frequency V.
From basic physics, wave obey the general equation
C = v y
4.What are the Components of Remote Sensing ?
5.What is Electromagnetic radiation?
Electromagnetic (EM) radiation is a self-propagating wave in space or through matter. EM radiation has an electric and magnetic field component which oscillate in phase perpendicular to each other and to the direction of energy propagation.
6.Write the type of Electromagnetic radiation?
Electromagnetic radiation is classified into types according to the frequency of the wave, these types include (in order of increasing frequency): radio waves, microwaves, terahertz radiation, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.
7.Draw the quantum theory interaction?
A quantum theory of the interaction between electromagnetic radiation and matter such as electrons is described by the theory of quantum electrodynamics.
8.Write about refraction?
In refraction, a wave crossing from one medium to another of different density alters its speed and direction upon entering the new medium.
The ratio of the refractive indices of the media determines the degree of refraction, and is summarized by Snell's law. Light disperses into a visible spectrum as light is shone through a prism because of refraction.
9.Draw the Wave model?
10.Write Planck's equation?
The frequency of the wave is proportional to the magnitude of the particle's energy. Moreover, because photons are emitted and absorbed by charged particles, they act as transporters of energy.
The energy per photon can be calculated by Planck's equation:
where E is the energy, h is Planck's constant, and f is frequency.
11.What is Black body ?
By definition a black body is a material that absorbs all the radiant energy that strikes it. A black body also radiates the maximum amount of energy, which is dependent on the kinetic temperature.
12.Write Stefan Boltzman law?
According to the Stefan-Boltzman law the radiant flux of a black body, Fb, at a kinetic temperature, Tkin, is Fb = s* Tkin 4 where s is the Stefan- Boltzman constant, 5.67*10-12 W*cm-2* o K-4.
13.What is emissivity?
Emissivity is a measure of the ability of a material to both radiate and absorb energy. Materials with a high emissivity absorb and radiate large proportions of incident and kinetic energy, respectively (and vice-versa).
14.Write Wein's Displacement law?
For an object at a constant temperature the radiant power peak refers to the wavelength at which the maximum amount of energy is radiated, which is expressed as lmax. The sun, with a surface temperature of almost 6000 o K, has its peak at 0.48mm (wavelength of yellow). The average surface temperature of the earth is 290 o K (17 o C), which is also called the ambient temperature; the peak concentration of energy emitted from the earth is at 9.7mm.This shift to longer wavelengths with decreasing temperature is described by Wien's displacement law, which states:
lmax = 2,897mm o K /Trad o K
15.Write Planck's Law?
The primary law governing blackbody radiation is the Planck Radiation Law, which governs the intensity of radiation emitted by unit surface area into a fixed direction (solid angle) from the blackbody as a function of wavelength for a fixed temperature. The Planck Law can be expressed through the following equation.
16.What is Scattering?
Scattering occurs when particles or large gas molecules present in the atmosphere interact with and cause the electromagnetic radiation to be redirected from its original path. How much scattering takes place depends on several factors including the wavelength of the radiation, the abundance of particles or gases, and the distance the radiation travels through the atmosphere. There are three (3) types of scattering which take place.
17.What are the types of scattering?
(i) Rayleigh scattering occurs when particles are very small compared to the wavelength of the radiation.
(ii) Mie scattering It occurs when the particles are just about the same size as the wavelength of the radiation.
(iii) Non Selective Scattering
The final scattering mechanism of importance is called nonselective scattering. This occurs when the particles are much larger than the wavelength of the radiation.
18.What is Atmospheric Windows?
The areas of the spectrum which are not severely influenced by atmospheric absorption and thus, are useful to remote sensors, are called atmospheric windows.