Properties%20of%20Light

1
Properties of Light

• Waves, particles and EM spectrum
• Interaction with matter
• Absorption
• Reflection, refraction and scattering
• Diffraction and polarization

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EM Wave
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Light waves
Complex light
Single wave monochromatic light
Coherent light laser
Polarized light
4
Electromagnetic spectra
High frequency EM acts like a particle
Low frequency EM acts like a wave
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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

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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

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Absorption depends on wavelength
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Absorption depends on frequency
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Water absorbs red faster than blue
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Speed of light depends on media
Speed of light is slower in water than in air
(opposite to sound)
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Light reflects and refracts
air
water
Snells law n1sinq1 n2sinq2 where ni
refractive index
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Refraction
http//micro.magnet.fsu.edu/primer/java/refraction
/index.html
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Reflectance
Diffuse (dull, matte)
Specular (shiny)
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Large angle causes internal reflections
air
water
cell
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Scatter depends on wavelength
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Sun is yellow, sky is blue
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Polarized Light
http//micro.magnet.fsu.edu/primer/java/polarizedl
ight/filters/index.html
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Polarized light indicates solar position
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Refraction depends on frequency
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Lenses focus light
http//micro.magnet.fsu.edu/primer/java/magnify/in
dex.html
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Mammalian Eye
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Far and near sightedness
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Light Diffraction
http//webphysics.ph.msstate.edu/javamirror/ipmj/j
ava/slitdiffr/
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Color
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Color Spectra
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Color has 3 dimensions
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Light interference