Using Prentice's rule, if a lens has power 4 D and is decentered by 1 cm, the induced prism is

Using Prentice's rule, if a lens has power 4 D and is decentered by 1 cm, the induced prism is

• A. 1 prism diopter
• B. 4 prism diopters
• C. 2 prism diopters
• D. 8 prism diopters

Answer: (B)

Prentice's rule says that decentering a lens from the optical center induces prism whose magnitude is the product of the lens power and the decentration distance (in centimeters). Here, the lens power is 4 diopters and the decentration is 1 cm, so the induced prism is 4 × 1 = 4 prism diopters. The direction of the prism depends on the decentration direction and lens sign, but the amount is 4 prism diopters.

Prentice's rule says that decentering a lens from the optical center induces prism whose magnitude is the product of the lens power and the decentration distance (in centimeters). Here, the lens power is 4 diopters and the decentration is 1 cm, so the induced prism is 4 × 1 = 4 prism diopters. The direction of the prism depends on the decentration direction and lens sign, but the amount is 4 prism diopters.