American Board of Opticianry (ABO) Practice Test

What is the total power of a lens with a +6.00 diopter front surface and a -4.25 diopter back surface lens?

1. a biconvex lens

2. +1.75

3. two plus surfaces

4. 1.75 diopters

The correct answer is: +1.75

A A biconvex lens is a lens that has two convex surfaces. While this describes the shape of the lens, it does not provide any information on the total power of the lens. C: Two plus surfaces would indicate that both surfaces of the lens have positive diopter values. However, the question specifies a +6.00 diopter front surface and a -4.25 diopter back surface, so this option is incorrect. D: 1.75 diopters is the sum of the two diopter values given in the question (+6.00 and -4.25), but this does not reflect the total power of the lens. The correct answer should take into account the two surfaces and their respective diopter values. B: The correct answer is +1.75. To find the total power of a lens, we need to add the power of the two surfaces. In this case, we would add +6.00 and -4.25, which gives us a total power of +1.75. This is the power that would be specified when ordering the lens. Therefore, option B is the correct answer.