Chp' 34 Electromagnetic waves slide 1

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• Chapter 34
• Electromagnetic waves

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• Light Wave or particle nature??
• IIsaac Newton - particle theory
• Reflection refraction
• CChristian Huygens wave theory
• TThomas Young wave theory
• Interference behaviour
• AAugustin Fresnel wave theory
• Interference diffraction
• HHeinrich Hertz particle theory
• Photoelectric effect
• JJames Maxwell electromagnetic waves
• AAlbert Einstein photons (energy packets)
• In some cases light acts as a wave and in others
  it acts like a particle
• Geometrical optics The description of light
  based on the straight line propagation of linear
  rays.
• Physical optics The description of light based
  on its wave nature.

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Reflection and Refraction (34  7)   Normal a
line that strikes a surface perpendicularly
(90o)   Reflection The reflected ray lies in
the same plane as the incident ray and the angle
(?) the reflected rays makes with the normal is
the same as the angle (?) the incident ray makes
with the normal.  
?    ? ? Law of Reflection
Refraction Change of direction when passing
through the boundary between two materials with
different refractive indices.
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  Example Yellow light has a wavelength of 400nm
in air. (nair 1.00029, nwater 1.333) (1)
Calculate the wavelength (in nm) of this light in
water. (2) Calculate the speed (in cm s-1) of
this light in water.   (1) ?water/?air  nair/n
water (?2/?1  n1/n2) ?water  ?air (nair/nwate
r) ?water  400 x 10-9 (1.00029/1.333) ?water 
 3.0 x 10-7 m ?water  300 nm   (2) vwater  v
air/nwater vwater  3 x 108 m.s-1/1.33 vwater 
 2.25 x 1010 cm.s-1
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cos?refracted  500 m/(length of hypotenuse) The
light beam must travel 590 m before it reaches
the bottom.
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A) total internal reflection B) partial
reflection from each surface C) variation of
index of refraction with wavelength D) a
decrease in the speed of light in the glass
E) selective absorption of various colors
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Answer Key   1. B 2. B 3. D 4. C 5. D
6. E 7. D 8. C 9. A 10. C 11. C 12. C
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