Sunday, May 21, 2006


3. Lens Systems

Objects and Images for Lens Systems (Figure 3)

  • Real objects have diverging rays and are on the same side as the incoming object rays.

  • Virtual objects are not naturally occurring and have converging rays.

  • Real images have a focal point that can be focused on a screen and therefore are on the same side as the outgoing image rays.

Click on image to enlarge.

Virtual images cannot be focused on a screen and are always on the left side of the lens system.

  • A virtual object may also have a virtual image.

  • When light rays are about to cross, they are considered to have positive (+) vergence (convergence) and when they are receding from their crossing point, they are said to have negative (-) vergence (divergence).

  • Rays that cross at the focal point of the lens are considered to have an infinite amount of vergence. Therefore rays that are parallel (have no crossing point), has a vergence of zero.

  • Converging lenses have real/inverted images that are on the opposite side of the lens from the object.

  • Diverging lenses create virtual/erect images that are on the same side as the object.


Post a Comment

<< Home