Worksheet 5: .

Radius of curvature

    Surface one is concave, has a radius of curvature of 50 mm, and is made from crown glass. Surface two is convex, is made of the same material, but has a radius of curvature of 0.5 m.

  1. Surface one has less curvature (is flatter) than surface two.
    Surface one has more curvature (is steeper) than surface two.

  2. The power of surface one (radius of 50 mm) is
    D

  3. The power of surface two (radius of 0.5 m) is
    D

    4. Nominal Power formula

  4. What is the power of a lens based on?

    .
  5. If a meniscus lens has a front surface power of 10.50 and a back surface power of 1.00, what is the nominal power of the lens?
    D
    .
  6. If I need a lens power of +1.25, and I choose to place it on a lens with a front surface of +6.25, what back surface power will I need?
    D
    .
  7. If the back surface power of a lens is -4.50 and the lens has a nominal power of +8.25, what will the front surface power be?
    D

    8. Lensmakers Equation

    A bi-concave lens is made out of a material with an index of refraction of 1.66. The radius of curvature for the front surface is 33 cm, and the radius of curvature of the back surface is 66 mm.

  8. Which surface is steeper?
    The front surface is steepest.
    The back surface is steepest.
    .
  9. Which surface has more power?
    The front surface has the most surface power.
    The back surface has the most surface power.
    .
  10. The nominal power of this lens is
    D
    .

That is all for this week.

Close the window (click the little x in the upper right-hand corner) if you came here directly from the assignment page.


Textbooks:
Brooks & Borish, Systems for Ophthalmic Dispensing, 2nd Ed, Butterworth-Heinemann, 1996
Stoner, Optical Formulas Tutorial, Butterworth-Heinemann, 1997

Copyright 1998 - 2001, Ellen Stoner, MALS, ABOM, NCLC
Registered students may print one copy for study purposes.