The Interaction of Light and Matter

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Reflection and Refraction of Light
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The Interaction of Light and Matter
Absorption, Transmission, and Reflection

• The opaque material in this candleholder only
  absorbs and reflects lightno light passes
  through it.

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Reflection and Refraction of Light
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Absorption, Transmission, and Reflection
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Reflection and Refraction of Light
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Absorption, Transmission, and Reflection
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Reflection and Refraction of Light
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Reflection of Light
Regular and Diffuse Reflection

• A smooth, even surface such as a pane of glass
  produces a sharp image by reflecting parallel
  light waves in only one direction.

• Reflection of light waves from a smooth surface
  is regular reflection.

• To cause a regular reflection, the roughness of a
  surface must be less than the wavelengths it
  reflects.

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Reflection and Refraction of Light
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Regular and Diffuse Reflection

• Reflection of light from a rough surface is
  diffuse reflection.

• Diffuse reflection is a type of scattering that
  occurs when light waves traveling in one
  direction are made to travel in many different
  directions.

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Reflection and Refraction of Light
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Refraction of Light

• Refraction is caused by a change in the speed of
  a wave when it passes from one material to
  another.

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Reflection and Refraction of Light
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Refraction of Light

• Index of refraction is the ratio of the speed of
  light in a vacuum to the speed of light in the
  material.

• The index of refraction indicates how much the
  speed of light is reduced in the material
  compared to its speed in empty space.

• The larger the index of refraction, the more
  light is slowed down in the material.

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Reflection and Refraction of Light
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Refraction of Light

• White light, such as sunlight, is made up of
  light waves with range of wavelengths.

• Prism refracts the light twiceonce when it
  enters the prism and again when it leaves the
  prism.

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Reflection and Refraction of Light
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Refraction of Light

• The longer wavelengths of light are slowed less
  and are bent the least.

• As a result, the different colors are separated
  when they emerge from the prism.

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Reflection and Refraction of Light
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Mirages

• Mirages result when the air at ground level is
  much warmer or cooler than the air above.

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Reflection and Refraction of Light
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Mirages

• The density of air increases as air cools and
  light waves move slower in cooler air than in
  warmer air.

• Light waves are refracted as they pass through
  air layers with different temperatures.

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Section Check
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Question 1
What happens to light waves that strike an object?
Answer
Light waves that strike objects can be absorbed,
reflected, or transmitted.
FL SC.A.2.4.6
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Section Check
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Question 2
What is the difference between refraction and
reflection?
Answer
Refraction occurs if a light wave changes speed
in moving from one material to another.
Reflection occurs when light waves are returned
or thrown back from a surface.
FL SC.A.2.4.6
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Section Check
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Question 3
__________ material only absorbs and reflects
light no light passes through.
A. Transparent B. Translucent C. Opaque D. Mirage
FL SC.A.2.4.6
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Section Check
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Answer
The answer is C. Transparent and translucent
materials both allow some light to pass through.
FL SC.A.2.4.6