# Diopters homework problem

1. May 28, 2008

### lostfan176

1. The problem statement, all variables and given/known data

A prescription for a corrective lens calls for +1.50 diopters. The lensmaker grinds the lens from a "blank" with n = 1.46 and a preformed convex front surface of radius of curvature of 19.0 cm. What should be the radius of curvature of the other surface?

2. Relevant equations

$$\frac{1}{f} = (n-1)\left ( \frac{1}{R_1} - \frac{1}{ R_2} \right )$$

3. The attempt at a solution

1.5=(1.46 - 1)(1/19 - 1/x)

(1.5/.46) - 1/19 = 3.208
-1/3.208 = -.3117

which is wrong
am i doing this right cause i dont think i am

2. May 29, 2008

### alphysicist

Hi lostfan176,

One thing I see: the value in diopters of a lens is the inverse of the focal length in meters. When you wrote 1/f=1.5, you chose your units of length in meters, but then you wrote R1 in centimeters.

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