American Board of Opticianry (ABO) Practice Test

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Prepare for the ABO certification with our comprehensive test preparation resources. Engage with interactive quizzes and detailed questions created specifically for the ABO exam. Enhance your understanding of opticianry concepts and ace your certification test!

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What is the focal length of a +4.00 diopter lens?

15 cm
25 cm
35 cm
45 cm

The correct answer is: 25 cm

The focal length of a +4.00 diopter lens is 25 cm. Diopters are a unit of measurement used to describe the optical power of a lens, and they are equal to the reciprocal of the focal length measured in meters. As the diopter value increases, the focal length decreases, resulting in a more strongly converging lens. Therefore, options A, C, and D are incorrect because they have larger focal lengths and lower diopter values. In contrast, option B has a smaller focal length and a higher diopter value, making it the correct answer.