Difference between revisions of Optics related math

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From 20/20 prescription: got a bit sloppy with signs
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For differentials to use a screen at, say, 50cm, just use <math>\frac{1}{f} = \frac{1}{0.50} + -\frac{1}{0.20} = -3D</math>.
For differentials to use a screen at, say, 50cm, just use <math>\frac{1}{f} = \frac{1}{0.50} + -\frac{1}{0.20} = -3D</math>.
(Which is consistent with the previous version, subtracting 2D from the full correction of -5D.)
(Which is consistent with the previous version, adding 2D to the calculated full correction of -5D.)


==Point of refraction==
==Point of refraction==