Effects of Media GAVRT Chapter 4

Atmospheric Windows Atmospheric windows are frequencies at which atmosphere allows em waves to pass Other frequencies are absorbed by atmosphere Optical window Radio window (5 MHz-300 GHz)

Absorption and Emission Lines Single frequencies of EM waves emitted as electron jumps from one energy level to another in atom. Absorption lines produced when cool gas in line of sight with black body Emission lines produced when cool gas is not in line of sight with black body Each element has unique set of lines Spectral Production picture of page 31 of text

Reflection Bouncing of wave off of boundary Angle of incidence equals angle of reflection Parabolic reflector of radio telescope Advantage of Cassegrain design Law of reflection diagram, page 34

Refraction Bending of waves when they pass from one medium to another (change speed) Index of refraction Of vacuum Other media Refraction in the atmosphere Prolonged sunsets Mirages Scintillation

Interference Occurs when two waves are at the same space at the same time Constructive interference results when waves in phase and produces larger waveform Destructive interference results when waves are out of phase and produces smaller waveform Constructive and destructive diagram page 37 of text

Diffraction Bending of wave without changing its speed Occurs when wave passes through opening or around edge of object Slit experiment and explanation Dark areas where destructive interference occurs Light areas where constructive interference occurs Single slit picture, Hewitt interference picture

Faraday Rotation Electric field will feel force from parallel magnetic field. Force is perpendicular to both fields causing electric field to rotate. Result is linearly polarized EM wave becoming circularly polarized wave.