Properties of Light (PowerPoint download) by jennyyingdi

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									     Properties of Light

• Waves, particles and EM spectrum
• Interaction with matter
• Absorption
• Reflection, refraction and
  scattering
• Diffraction and polarization
EM Wave
Light waves
              Complex light



              Single wave =
              monochromatic
              light

              Coherent light =
              laser


              Polarized light
    High frequency EM
    acts like a particle



Electromagnetic
    spectra
    Low frequency EM
    acts like a wave
      Interaction with matter
• Color occurs when molecules selectively
  absorb light of specific wavelengths
• High energy, short wavelengths, disrupts
  chemical bonds
• Infrared radiation affects bond vibrations
  and is perceived as heat (snakes, vampire
  bats have heat sensors, but poor resolution)
• Light is selective absorbed and reradiated in
  a transparent medium
      Requirements for Vision
• Reflection off solid objects
  – Higher and lower frequencies pass through
• Straight-line transmission without scatter
  – Permits formation of spatial maps
• Refraction at the boundary of two media
  with different densities
  – Permits focusing and image formation by an
    eye behind a lens
Absorption depends on wavelength
Absorption depends on frequency
Water absorbs red faster than blue
 Speed of light depends on media




Speed of light is slower in water than in air (opposite to sound)
     Light reflects and refracts



                                                    air


                                                    water




Snell’s law = n1sinq1 = n2sinq2 where ni = refractive index
                     Refraction




http://micro.magnet.fsu.edu/primer/java/refraction/index.html
                        Reflectance




Diffuse (dull, matte)                 Specular (shiny)
Large angle causes internal reflections

                                  air


                                 water




                                  cell
Scatter depends on wavelength
Sun is yellow, sky is blue
                      Polarized Light




http://micro.magnet.fsu.edu/primer/java/polarizedlight/filters/index.html
Polarized light indicates solar position
Refraction depends on frequency
              Lenses focus light




http://micro.magnet.fsu.edu/primer/java/magnify/index.html
Mammalian Eye
Far and near sightedness
                Light Diffraction




http://webphysics.ph.msstate.edu/javamirror/ipmj/java/slitdiffr/
Color
Color Spectra
Color has 3 dimensions
Light interference

								
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