Chapter 16 Optical Phenomena

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Chapter 16 Optical Phenomena of the Atmosphere
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basic properties of light

• reflection,
• refraction,
• diffraction, and
• interference.

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Law of Reflection

• when light rays are reflected, they bounce off
  the reflecting surface at the same angle (the
  angle of reflection) at which they meet that
  surface (the angle of incidence).

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Law of Reflection
On Smooth Surface
On Rough Surface
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Internal reflection

• when light that is traveling through a
  transparent material, reaches the opposite
  surface and reflects back into the transparent
  material.

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Refraction

• is the bending of light due to a change in
  velocity as it passes obliquely from one
  transparent medium to another.

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Bending of Light
Refraction
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The bending of light

• by refraction is responsible for such common
  optical illusions as the apparent displacement of
  the position of the stars, Moon, and Sun.

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Mirages

• are an optical effect of the atmosphere caused by
  refraction when light passes from air with one
  density into air with a different density and the
  object appears displaced from its true position.

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Highway Mirage
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Hot Air Below Cool Air Objects Appearing
Upside Down
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inferior mirage

• occurs when the image appears below the true
  location of the observed object.
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Cool Air Below Warm Air Objects Appear Above
Their Positions
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Looming

• When objects appear to be suspended above the
  horizon.
• Looming is considered a superior mirage because
  the image is seen above its true position

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Apparent Displacement of Position of the Sun
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Towering

• Is a mirage that changes the apparent size of an
  object.

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Fata Morgana

• A type of towering that is observed in coastal
  areas as towering castles that appear out of thin
  air.

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Rainbows

• Require sunlight and water droplets.
• the observer must be between the Sun and rain
• water droplets act as prisms and refraction
  disperses the sunlight into the spectrum of
  colors, a process called dispersion.

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Formation of a Rainbow
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Primary rainbow

• sunlight is reflected once within a raindrop.
• In a secondary rainbow, light is reflected twice
  within a raindrop before it exits.

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The Visible Spectrum
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Rainbow
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Secondary Rainbow
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Halo

• is a narrow whitish ring with a large diameter
  centered on the Sun.
• are produced by dispersion of sunlight from
  atmospheric ice crystals that refract light.
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25
Common Ice-Crystal Configurations
Path Taken by Light to Generate Halos
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Halo Produced by Dispersion of Sunlight by
Cirrostratus Clouds
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sun dogs or parhelia

• mock suns.
• viewed near sunset or sunrise, is a vertical
  shaft of light that appears to extend upward from
  the Sun

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Sun Dogs (Parhelia)
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Sun Pillar
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Glory

• commonly seen by pilots,
• consists of one or more colored rings that
  surround the airplanes shadow projected on the
  clouds below.

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corona

• a bright whitish disk centered on the Moon or
  Sun.
• produced when water droplets scatter light from
  the illuminating body.

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The Corona
The Glory
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diffraction

• bending of light as it passes near the edges of
  cloud droplets.
• diffracted light will be directed into the
  shadow of the droplet.

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Multiple Distorted Images of Sun Form a Long,
Narrow Band
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Chapter 16

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