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Light and Reflection

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Light and Reflection Chapter 14, Sections 1 & 2 Pg. 520-539 Characterization of Light Light has both a wavelike and particle like nature. Electromagnetic wave theory ... – PowerPoint PPT presentation

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Title: Light and Reflection


1
Light and Reflection
  • Chapter 14, Sections 1 2
  • Pg. 520-539

2
Characterization of Light
  • Light has both a wavelike and particle like
    nature.
  • Electromagnetic wave theory Light is a wave
    composed of oscillating electric and magnetic
    fields (electromagnetic wave).
  • These waves propagate transversely at right
    angles to each other.

3
Characterization of Light
4
Characterization of Light
  • All electromagnetic waves travel at the speed of
    light (c).
  • c 3.0 x 108 m/s
  • Electromagnetic waves vary depending on frequency
    and wavelength.
  • These differences account for the broad range in
    the electromagnetic spectrum.

5
Electromagnetic Spectrum
6
Characterization of Light
  • The same relationship between frequency,
    wavelength, and speed that exists in sound waves
    or objects undergoing SHM also holds true for
    electromagnetic waves.

? f ? (Chapter 12)
c f ?
7
Characterization of Light
  • Huygens Principle
  • Electromagnetic waves travel in wave fronts.
  • Wave fronts are made up of many wavelets, each
    containing a point source. If you make a line
    tangent to each point source, you have identified
    a new wave front.

8
Characterization of Light
  • Huygens Principle describe waves interacting
    with matter (diffraction) or waves moving in a
    straight line.
  • The perpendicular direction in which the wave
    front is moving is referred to as a ray.

9
Characterization of Light
Wave front motion as it moves around an object
10
Characterization of Light
  • Light becomes more spread out and there is less
    light available per unit area.
  • Inverse relationship between brightness and
    distance.
  • Brightness decreases by the square of the
    distance from the source.
  • ex. There is ΒΌ as much light falling on a
    particular spot 2 m away than there is light
    falling on the same spot that is 1 m away. (fig
    14-4 pg. 525)

11
Reflection
  • The turning back of an electromagnetic wave
    (light ray) at the surface of a substance.
  • Depending on how smooth the reflecting surface
    is, the reflection will either be diffuse or
    specular.

12
Reflection
  • Reflections off flat surfaces follow 2 simple
    rules
  • angle in (incidence) equals angle out
    (reflection)
  • angles measured from the surface (normal)

13
Reflection
  • Using the basic rules of reflection, we can
    create virtual images.
  • Virtual images are images formed by light rays
    that appear to intersect.
  • ex. Looking in a mirror
  • Image location can be predicted with ray
    diagrams.

14
Reflection
Ray diagram of mirror image (full length mirror)
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