22.1) The Nature of Light

  Newton said light is made of particles.
  
  Young said light consists of waves.
  
  Maxwell - speed of light is 3.0 x 108 m/s
  
  Einstein - energy of a photon
  
  E = hf
  
  Where E is the Energy, h is Planck's constant (2.23 x 10-34J s)
  and f is the frequency
  
  In some cases light acts as a wave and in others it acts as a particle.
  
  
  
22.2) Measurements of the speed of light

  Roemer's method - approximated the speed of light by observing the
  orbit of the moons of Jupiter
  
  Fizeau's technique - approximated the speed of light using a spinning wheel
  with teeth and a mirror.
  
22.3) The Ray Approximation in Geometric Optics

  Light travels in a straight line path until it encounters a boundary 
  between two different materials.
  
22.4) Reflection and Refraction

  specular reflection - from a smooth surface
  
  diffuse reflection - from a non-smooth surface
   
  From now on, when we say reflection in this class, we mean specular 
  reflection
   
  the angle of reflection equals the angle of incidence, or
   
  θ'1 = θ1 
   
  This can cause the 'red eye' effect if the flash is close to the lens.
  
Refraction of light:

  sinθ1/sinθ2=v2/v1
  
  where v2 is the speed of light in material 2 and v1 is the
  speed of light in material 1.
  
  The path of light through a refracting surface is reversible.
  
22.5) The Law of Refraction
  
  index of refraction:
  
  n = speed of light in a vacuum/speed of light in a medium = c/v
  
  as light travels from one medium to another its wavelength does not change.
  
  Snell's Law:
  
  n= λ0/λ1
  
  n1 sin θ1 = n2 sin θ2 
  
  Where n is the index of refraction for the material and θ is the angle
  with the perpendicular.
  
22.6) Dispersion and Prisms  

  Light of different wavelengths is bent at different angles when incident on
  refracting material.  The index of refraction decreases with increasing
  wavelength.
  
  ROY-G-BIV - red has the largest wavelength, violet has the smallest.
  
22.7) The Rainbow  
  
  The dispersion principal as discussed in 22.6 is what causes a rainbow.
  
22.8) Huygen's Principle  
  
  Uses moving spheres to model the motion of light.  (picture on p. 739)
  
22.9) Total Internal Reflection

  It is possible for θ2, the angle of refraction, to be
  >= 90 degrees.  If the angle is > 90 degrees, that is called total
  internal reflection.
  
  To find θc, the critical angle, defined as 90 degrees,
  we can use Snell's law.  Remember, the sin(90 degrees) = 1.
  
  sin θc = n2/n1
  
  Application: fiber optics
  
  Light is reflected off the edges of the fiber allowing it to bend around
  corners and curves.
  
  Doctors use to see inside the human body.
  
  Phone companies use to send signals.  The higher wavelength of light (as 
  compared to electricity) allows it to carry a much higher volume of 
  information.  It also travels faster.
  
  
  
  
  
HW 7:
p. 745 M.C. # 1,   
p. 746 C.Q. #10, Problem # 1
p. 747 # 5 
p. 749 # 26, 31