Lecture 2: Electromagnetic Radiation
Instructor: Gregory A. Carter, Ph.D.
Institution: The University of Southern Mississippi
Altered when it interacts with objects, carrying information about them.
Requires understanding of radiation and its interaction with materials.
Comprised of electromagnetic waves exhibiting wave-particle duality:
Wave properties
Particle properties (photons)
Generated by accelerated electric charge.
Varies based on production mechanisms:
Gamma radiation: atomic nucleus decay
Light, UV, X-rays: electron orbit transitions
Infrared radiation: molecular vibrations/rotations
Radio waves: oscillations of electric currents in antennas.
In the 1860s, EMR was conceptualized as a wave traveling at speed of light (c = 3 x 10^8 m/s).
Composed of two fluctuating fields: electric and magnetic, at right angles to each other.
Plane polarized: when the electric field is in a fixed plane.
Characteristics depend on:
Wavelength (位): distance between points on a wave; varies from long AC waves to short gamma waves.
Frequency (谓): number of oscillation cycles per unit time.
All travel at speed of light in a vacuum (c = 3 x 10^8 m/s); no theoretical limits on 位 or 谓.
Relationship: c = 位谓.
Wavelengths and Frequencies:
Vary from gamma rays (10^-12 m) to radio waves (kilometers long).
Visible Spectrum: 位 = 400 nm to 700 nm.
Proposed by Niels Bohr and Max Planck.
Energy transferred in discrete packets (quanta or photons).
Energy equation: E = h谓; E is higher at higher frequencies and shorter wavelengths.
Planck constant (h = 6.626 x 10^-34 J路s).
Radiant Energy: Joule (J).
Examples of photon energy:
UV (位 = 254 nm): 471 kJ/mol
Blue (位 = 460 nm): 260 kJ/mol
Red (位 = 700 nm): 176 kJ/mol.
Radiant Flux: Watt (W) = Js^-1.
Base Quantities:
Length: meter (m)
Mass: kilogram (kg)
Time: second (s)
Derived Quantities:
Area: m虏
Volume: m鲁
Frequency: Hertz (Hz)
Energy: Joules (J).
Jensen, J. R. (2007). Remote Sensing of the Environment.
National Institute of Standards and Technology.
Rees, W.G. (2013). Physical Principles of Remote Sensing.
Rossotti, H. (1983). Colour: Why the World Isn鈥檛 Grey.