LENS

					             Refraction with Lenses
- importance -viewing the world on various levels
microscopes to telescopes, projecting, magnifying, photographing
Correcting vision - glasses, contact lenses, eye surgery
- the bending of light is due to a change in velocity and wavelength as
light moves from the air to glass and back to air
- the light is bent twice
- 2 types of lenses: Converging(convex)           Diverging (concave)
               Refraction with Lenses
                                       Focal
Principle                              Length
axis


            Focal Point                     Focal Plane

 For a lens there are two focal points and two focal planes.
 Two types of images can be formed:
        Real image - an inverted image on the side opposite the object
               side of the lens. Real image is projected.
        Virtual image - upright image formed on the same side as the
                object, not projectable. Must look through lens.
To determine the size and type of image(real or inverted)
construct a ray diagram by drawing 2 of 3 possible rays.

  1. Parallel to primary axis and then through focal point.

  2. Straight through center of the lens
  3. Through focal point on object side, through lens then
                parallel to primary axis.




                                              Real Image
To determine the size and type of image (real or virtual)
construct a ray diagram by drawing 2 of 3 possible rays.

  1. Parallel to primary axis and then through focal point.

  2. Straight through center of the lens
  3. Through focal point on object side, through lens then
               parallel to primary axis.




      Virtual
      Image
Diverging Lens
  1. Parallel to primary axis and through the lens as if it
         had come from the focal point.

  2. Straight through center of the lens

  3. Ray heading to focal point on far side is refracted so it
         emerges parallel to primary axis.




                  Virtual
                  image

				
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posted:5/2/2011
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