1. A surface is made from crown glass, and has a radius of curvature of 85 mm. If the surface is in air, what is its surface power?
 
•                  n - 1

       D = --------
                    r
where:
   D =
   n =
   r =   in meters
 
•    D = ?

   n = 1.523
   r = 85 mm = 0.085 m
 
•               1.523 - 1

       D = ------------
               0.085 m
               0.523
       D = -----------
               0.085

   D = 6.15 D
 

2. A surface with radius of curvature of 15 cm is made from polycarbonate. If the surface is in air, what is its surface power?
•                  n - 1

       D = --------
                    r
where:
   D =
   n =
   r =   in meters
 
•    D = ?

   n = 1.586
   r = 15 cm = 0.15 m
 
•               1.586 - 1

       D = ------------
               0.15 m
               0.586
       D = -----------
                0.15

   D = 3.91 D
 

3. What is the surface power in air of a curve with radius 1 m, if it is made from a material with index of refraction of 2.0?
•                  n - 1

       D = --------
                    r
where:
   D =
   n =
   r =   in meters
 
•    D = ?

   n = 2.0
   r = 1 m
 
•                2.0 - 1

       D = ------------
                1 m
                 1.0
       D = -----------
                   1

   D = 1.00 D

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