answers to nominal power exercises

Answers to nominal power formula problems.

Find the nominal power if:

D1 = +10.00 and D2 = -6.00 DN = +4.00 D
D1 = +2.00 and D2 = -4.50 DN = -2.50 D
D1 = +8.00 and D2 = -5.75 DN = +2.25 D
D1 = -1.25 and D2 = -3.75 DN = -5.00 D
D1 = -5.00 and D2 = -6.00 DN = -11.00 D

Find the back surface if

DN = +10.00 and D1 = +6.00 D2 = +4.00 D
DN = +2.00 and D1 = +8.50 D2 = -6.50 D
DN = +8.00 and D1 = +5.75 D2 = +2.25 D
DN = -5.00 and D1 = -1.00 D2 = -4.00 D
DN = +6.50 and D1 = +10.00 D2 = -3.50 D

Find the front surface if

DN = +10.00 and D2 = -2.00 D1 = +12.00 D
DN = +2.00 and D2 = -8.50 D1 = +10.50 D
DN = +8.00 and D2 = -2.75 D1 = +10.75 D
DN = -1.25 and D2 = -7.75 D1 = +6.50 D
DN = -5.00 and D2 = -3.00 D1 = -2.00 D
DN = +6.50 and D2 = -10.00 D1 = +16.50 D

I need a lens with power +3.50D. If I use a lens blank with a front surface of +8.00D, what back surface do I need to make?

D2 = DN - D1 = +3.50 - (+8.00) = -4.50 D

I have a lens with a front surface of +9.25D and a back surface of -2.25D. What is the power of the lens?

DN = D1 + D2 = +9.25 + (-2.25) = +7.00 D

I want my lens to have a power of -3.00D. What back surface do I need if the front surface is +8.00D

D2 = DN - D1 = -3.00 - (+8.00) = -11.00 D

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