A closer look at light

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A closer look at light
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Energy

• All matter contains energy in one form or
  another.
• It can be transferred from one object to another,
  but is never destroyed (Law of Conservation of
  Energy).

• Comes in many forms, including light energy.
• Other forms of energy include sound, chemical,
  kinetic, mechanical, etc.

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Think

• What do these light sources have in common?

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Yes, they are both hot!

• Heat and light often coexist. A light bulb gets
  hot when its illuminated. A flame is also hot.
  Can you think of other times when heat and light
  coexist?

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Comparing Light and Sound
Remember that sounds came in a wide range of
wavelengths
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The Electromagnetic Spectrum

• Youve already learned that visible light is part
  of the electromagnetic spectrum, but what does
  this mean?

• An electromagnetic wave is a form of energy that
  can travel through empty space as well as matter.
  
• Other examples x-rays, radio waves

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Are sound waves part of the electromagnetic
spectrum? Why or why not?
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NO!!!

• They cant travel through space (a vacuum).

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How Light Travels

• Spreads out in all directions from its source
• In straight lines, called rays
• Refracts as it passes from one substance to
  another
• Can travel in a vacuum
• Speed of light
• 186,000 miles per second (in space)
• Fastest thing we know of
• New York to San Francisco 62 times per sec.

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3 things can happen when light hits a surface.
Reflected absorbed pass through
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The Law of Reflection
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The Law of Reflection

• Light will always be reflected by a surface
  at the same angle at which it hits the surface.

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Law of Reflection - Specular Reflection

• When light reflects off of smooth surfaces, the
  law of reflection is clearly demonstrated.

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Law of Reflection - Diffuse Reflection

• Though it is not as clear, the law of reflection
  is also demonstrated on rough surfaces.
• Think of a rough surface as many small, smooth
  surfaces at different angles.

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Reflection Activities
In your lab groups, complete the activities in
the packet which I am providing. Please handle
the mirrors VERY CAREFULLY! If one breaks, I will
clean it up.
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Transmission-

• When light passes through an object

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Transmission is easier with some materials than
it is with others.

• Transparent - materials that allow all light to
  pass through (air, glass, water)
• Translucent - materials that dont transmit all
  of the light (wax paper)
• Opaque - materials that dont allow any light to
  pass through (your desk)

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Refraction

• Light bends when it passes from one material into
  another.

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Finally

• Absorption

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Absorption

• An apple looks red because it absorbs every
  color except red. (It reflects red.)
• White - absorbs none
• Black - absorbs all

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Adding Light
When you mix light, the combination of colors is
different than when you mix paints.
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Related Vocabulary

• Use your Sciencesaurus, textbook, or notes to
  define the following terms. Write your
  definitions on page ___
• Photon
• Prism
• Index of Refraction
• Angle of Incidence
• Angle of Reflection
• Normal angle