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optics

VIEWS: 4 PAGES: 47

  • pg 1
									  Optics
Chapter 17 & 18
        Topics for Optics
• Reflection of Light • Refraction of Light
  – Law of Reflection     – Law of refraction
  – Plane Mirrors         – Convex lenses
  – Concave Mirrors       – Concave lenses
  – Convex Mirrors
                        • Optical Instruments
          Law of Reflection
• All mirrors obey the Law of reflection
• The angle of incidence equals the angle of
  reflection
     Law of Reflection (Cont.)
• It does not matter the shape of the mirror, the
  angle of reflection will still equal the angle of
  incidence.
   Image Types:
•Real or Virtual
•Upright or Inverted
•Reduced or Enlarged
         Real or Virtual
• Real: image      • Virtual: image
  projected on a     can only be seen
  screen             inside the mirror
       Upright or Inverted
• Upright: Image is   • Inverted: Image is
  oriented the same     oriented the
  direction as the      opposite direction
  object                as the object
       Reduced or Enlarged
• Reduced: image is      • Enlarged: image is
  smaller in size then     larger in size then
  the object.              the object.
                Plane Mirrors
• The image formed by plane
  mirrors can only be seen
  behind the mirror.
• This is known as a virtual
  image.
• Image is the same size as the
  object.
• Only the right and left of the
  image is changed.
                   Curved Mirrors
• They can be considered cut outs of a spherical mirror
• Curved mirrors can be either
   – concave (making a little cave)
   – convex (vexing out in the middle)
          Location of Image




• do = distance of object
• di = distance of image
• f = focal length
Concave Mirrors Converge
     Rays of Light
           Ray Tracing Basics
• All rays parallel to the
  principle axis will go
  through the focal point.
• The rays are also
  reversible, so if they
  start at the focal point,
  they will hit the mirror
  and go parallel to the
  principle axis.
         Ray Tracing Basics




• C: Center of Curvature
• F: Focal Point (1/2 of C)
                    Ray One:
Draw a parallel line from the top of the object to the
      mirror.
This line should bounce off the mirror and through the
      focal point.
                    Ray Two:
• Draw a line from the top of the object through the
     focal point to the mirror.
• This line should bounce off the mirror and go
     parallel to the principle axis.
                   Ray Three:
• Draw a straight line from the top of the object and
  through the Center of curvature.
Reviewing the
 three rays:
1. Parallel, then
   through f.
2. Through f, then
   parallel.
3. Straight line through
   top of object and C.
Final step: Draw the image where the
3 lines converge…




Make sure the bottom of the image is on the principle axis,
and the top of the image is at the convergence point.
         Distant Objects:
• The image of a distant object will
  form at the focal point of the concave
  mirror and be very very small.
                Objects At C:
The Image will be:
• Real               Same location as object
• Inverted
• Same size
        Objects Between C and f:
The Image will be:
• Real               Image is located outside C
• Inverted
• Enlarged size
              Objects Inside f:
The Image will be:
• Virtual
• Upright
• Enlarged in size
Convex Mirrors Diverge
    Rays of Light
Ray Tracing for Convex Mirrors
• Very similar to ray tracing for concave
  mirrors, except the object is on the other
  side of the mirror than the Center of
  curvature and focal point…
                    Ray One:
Draw a parallel line from the top of the object to the
     mirror.
An imaginary line should be drawn from this point to
     the focal point.
                     Ray Two:
• Draw a line from the top of the object to the focal
  point on the other side of the mirror, but stop at the
  mirror.
• Draw a line parallel to the principle axis from the
  point where the previous line hits the mirror.
                   Ray Three:
• Draw a straight line from the top of the object and to
  the Center of curvature.
Reviewing the
 three rays:
1. Parallel, then
   through f.
2. Through f, then
   parallel.
3. Straight line through
   top of object and C.
Final step: Draw the image where the
3 lines converge…
Lenses
Converging Lens
   Rules For Converging Lenses
1) Any incident ray traveling parallel to the
   principal axis of a converging lens will refract
   through the lens and travel through the focal
   point on the opposite side of the lens.
2) Any incident ray traveling through the focal
   point on the way to the lens will refract through
   the lens and travel parallel to the principal axis.
3) An incident ray which passes through the center
   of the lens will in effect continue in the same
   direction that it had when it entered the lens.
Image Formation by Converging Lens
Diverging Lens
    Rules For Diverging Lenses
1) Any incident ray traveling parallel to the
   principal axis of a diverging lens will refract
   through the lens and travel in line with the focal
   point (i.e., in a direction such that its extension
   will pass through the focal point).
2) Any incident ray traveling towards the focal
   point on the way to the lens will refract through
   the lens and travel parallel to the principal axis.
3) An incident ray which passes through the center
   of the lens will in effect continue in the same
   direction that it had when it entered the lens.
Diverging Lens Image Formation




    Always Virtual, Smaller, and Right-Side Up
The Human Eye
The Human Eye
Normal Eye Focus
Near-Sighted (Myopia)
Far-Sighted (Hypermetropia)
              Astigmatism
• Cornea is oval shaped instead of spherical.
  This causes light to focus on two or more
  spots.
             LASIK

Laser-assisted In Situ Keratomileusis

								
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