How many optical centers would there be in a bifocal lens (non plano distance)?

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Multiple Choice

How many optical centers would there be in a bifocal lens (non plano distance)?

Explanation:
In a bifocal lens you effectively have two separate refractive zones: the distance portion and the near portion. Each zone behaves like its own little lens and has its own optical center—the point where light passes through undeviated for that zone. Because the two segments have different powers and are located at different spots on the lens, their optical centers do not coincide. Since the distance portion has finite power (non plano), it contributes its own center, and the near portion contributes a second center. So, there are two optical centers in a bifocal lens.

In a bifocal lens you effectively have two separate refractive zones: the distance portion and the near portion. Each zone behaves like its own little lens and has its own optical center—the point where light passes through undeviated for that zone. Because the two segments have different powers and are located at different spots on the lens, their optical centers do not coincide. Since the distance portion has finite power (non plano), it contributes its own center, and the near portion contributes a second center. So, there are two optical centers in a bifocal lens.

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