A lens with a focal length of 20 cm has what diopter value?

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Prepare for the Certified Paraoptometric Assistant (CPOA) Exam. Study with extensive flashcards and multiple choice questions with explanations. Enhance your skills and knowledge to succeed.

Multiple Choice

A lens with a focal length of 20 cm has what diopter value?

Explanation:
Diopters measure how powerful a lens is, calculated as the reciprocal of the focal length in meters. Convert the focal length to meters: 20 cm = 0.20 m. Then power = 1 / 0.20 = 5 diopters. The lens is converging (positive focal length), so the sign is positive. Therefore the correct power is +5.0 D. The other options would require different focal lengths or a negative sign (for a diverging lens).

Diopters measure how powerful a lens is, calculated as the reciprocal of the focal length in meters. Convert the focal length to meters: 20 cm = 0.20 m. Then power = 1 / 0.20 = 5 diopters. The lens is converging (positive focal length), so the sign is positive. Therefore the correct power is +5.0 D. The other options would require different focal lengths or a negative sign (for a diverging lens).

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