Home / Oral Pathology / TYPES OF LENSES


  • If the lens is biconcave or plano-concave, a collimated beam of light passing through the lens is diverged (spread); the lens is thus called a negative or diverging lens.
  • The beam after passing through the lens appears to be emanating from a particular point on the axis in front of the lens; the distance from this point to the lens is also known as the focal length, although it is negative with respect to the focal length of a converging lens.


  • The object is situated at the front focal plane of the convex lens. In this case, the rays of light emerge from the lens in parallel. When brought to focus by the eye, the image, on the SAME side of the lens as the object, appears upright.
  •      It is a ‘Virtual image’.

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