A lens with two diopters of power has what approximate focal length?

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Multiple Choice

A lens with two diopters of power has what approximate focal length?

Explanation:
Power in diopters is the reciprocal of the focal length in meters. So for a lens with 2 diopters, the focal length is f = 1/P = 1/2 = 0.5 meters. That’s why the focal length is about 0.5 m. In general, higher diopter values mean shorter focal lengths: 1 diopter would be 1 meter, 0.5 diopter would be 2 meters, and 4 diopters would be 0.25 meters.

Power in diopters is the reciprocal of the focal length in meters. So for a lens with 2 diopters, the focal length is f = 1/P = 1/2 = 0.5 meters. That’s why the focal length is about 0.5 m. In general, higher diopter values mean shorter focal lengths: 1 diopter would be 1 meter, 0.5 diopter would be 2 meters, and 4 diopters would be 0.25 meters.

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