W9_parallel_resonance.eps

Week 12: Lenses and Mirrors 405

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s s’

Figure 167: A converging lens with focal length of 10 cm and an object ats= 30 cm.

As before, if one puts an object inside the focal length it will make a magnified, erect,

virtual image, if one exchanges the position of object and image in the example above,

one will obtain an inverted, real image that is larger than the object.

A diverging lens, on the other hand, has only one generic diagram to be learned. It is

basically the same as for the mirror, except that rays are transmitted through the thin

lens (with all bending occurring at the thin plane representing the center plane of the

lens) instead of reflected from it. In the situation represented in figure (168), the image

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s’

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Figure 168: A diverging lens with focal length of−10 cm and an object ats= 20 cm.

is virtual, erect, and smaller than the original object. Show (from the numbers and thin

lens formula) thats′=− 6 .67 cm and thatm= 1/3.

12.5: The Eye

The eye is roughly spherical and approximately one inch in diameter. Figure (169) shows

its essential anatomy. Here is a brief review of the components of the eye.

• Cornea:The cornea of the eye is the rounded, transparent structure atthe front
  of the eye. It is strongly curved, and is responsible formostof the bending of light
  required to focus images onto the...


• Retina:The retina is the “film” of the eye. It consists of tight bundles of pho-
  tosensitive nerves calledrods(sensitive to light intensity) andcones(sensitive to
  intensity in specific colors. In the center of the retina is the...


• Macula: The macula is the most sensitive part of the retina and is where one
  ”sees” the object of one’s attention. It is more or less in front of the...