 The EM spectrum extends from gamma rays through radio waves. Remote sensing is carried out in a small portion of the entire spectrum.
Electromagnetic energy: a dynamic form of energy that is caused by the oscillation or acceleration of a charged particle. All substances above absolute zero (0 Kelvin, = –273.16°C) emit a range of electromagnetic energy. Practically all the natural electromagnetic energy injected into the earth system is produced by the sun.
Electromagnetic radiation: Stream of massless particles, traveling in a wave-like pattern, at the speed of light, each possessing a specific amount of energy. Electromagnetic radiation is simply electromagnetic energy in transit. It possesses two fluctuating fields – one electric and one magnetic.
Electromagnetic spectrum: The entire range of electromagnetic energy constitutes the electromagnetic spectrum. In this spectrum, the electromagnetic energy is arranged according to wavelength which is directly related to frequency.
Transmission: the process where electromagnetic radiation penetrates and passes through a material/medium.
Absorption: When electromagnetic radiation cannot transmit through a material, it may be blocked and absorbed by the particles in the material. This process of absorption increases the amount of energy in the material, which in turn raises the temperature of the material. Absorption and transmission are inversely related.
Reflection: the process where electromagnetic radiation passes through a medium, strikes a target and returns to the same medium through which it traveled. Often the term reflection is used to mean specular or mirror reflection, where the angle at which the electromagnetic radiations strike the target surface is equal to the angle at which they bounce back.
Scattering: when electromagnetic radiation falling on the target surface returns/bounces in different directions. Scattering can be construed to be multiple reflections of electromagnetic radiation by particles or surfaces.
Emission: process by which matter radiates/gives out electromagnetic energy. All matter warmer than 0 K (–273.16°C) emits electromagnetic energy. The higher the temperature of the body, the greater the emitted energy.
|
