Properties of Light Part 1

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Properties of LightPart 1
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Properties of Light

• Light travels in straight lines

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• Light travels VERY FAST around 300,000
  kilometres per second.

At this speed it can go around the world 8 times
in one second.
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• Light travels much faster than sound. For example

• Thunder and lightning start at the same time, but
  we will see the lightning first.

• 2) When a starting pistol is fired we see the
  smoke first and then hear the bang.

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• We see things because they reflect light into our
  eyes

Homework
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Reflection

• What does the term reflection mean?
• This occurs when a wave bounces off of a
  material.
• Light reflecting from an object is what makes it
  visible

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Reflection

• When light hits a surface, some of it bounces off
  or is reflected. Mirrors are very shiny surfaces
  designed to reflect nearly all the light that
  hits them.

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Reflection

• Reflection is most likely the property of light
  that we experience most often. Looking at
  yourself in a mirror, seeing the reflection of
  the sun in the ocean at sunset, and the sight of
  a mirage on the hot desert sand are all examples
  of reflection. In fact, everything you can see is
  the result of a complex pattern of light
  reflecting off the surface of something.

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• Shadows

Shadows are places where light is blocked
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color

• White light is not a single color it is made up
  of a mixture of the seven colors of the rainbow.

We can demonstrate this by splitting white light
with a prism This is how rainbows are formed
sunlight is split up by raindrops.
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The colors of the rainbow

• Red
• Orange
• Yellow
• Green
• Blue
• Indigo
• Violet

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Seeing color

• The color an object appears depends on the colors
  of light it reflects.

For example, a red book only reflects red light
White light
Only red light is reflected
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A pair of purple trousers would reflect purple
light (and red and blue, as purple is made up
of red and blue)
Purple light
A white hat would reflect all seven colors
White light
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Using colored light

• If we look at a colored object in colored light
  we see something different. For example,
  consider a football kit

Shirt looks red
White light
Shorts look blue
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Red light
Shirt looks red

• In different colors of light this kit would look
  different

Shorts look black
Shirt looks black
Blue light
Shorts look blue
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Red
White
Blue
Green
Magenta
Yellow
Cyan
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How do we see color?
Color originates in light. Sunlight, as we
perceive it, is colorless. In reality, a rainbow
is testimony to the fact that all the colors of
the spectrum are present in white light. As
illustrated in the diagram below, light goes from
the source (the sun) to the object (the apple),
and finally to the detector (the eye and brain).
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Refraction
What does the term refraction mean? Refraction
occurs when the path of light wave changes as it
moves from one material to another.
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The picture of the ruler appears to be broken,
even thought it is not. It appears broken because
light travels through water and glass at
different speeds. The light waves refract or
bends as they pass from water to glass to air.
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Refraction In Our World

• How is refraction put to good use?
• Devices that refract light include eyeglasses,
  contact lenses, cameras, microscopes, and
  telescopes.

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Review Questions for Test

1. Define the terms reflection and refraction.
2. Briefly discuss how we see color.
3. Name a tool that is used in our world to reflect
   light.

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Review continued

• 4. Name a tool in our world that refracts light?
• 5. In the picture of the ruler, what makes the
  ruler appear as if it is broken?