Problem 25.24: Bifocals, I. A person can focus clearly only on objects between 3

Question

Problem 25.24: Bifocals, I. A person can focus clearly only on objects between 37.5cmand 51.0cm from his eyes. Part A Find the focal lengths of the correcting contact lenses needed to correct his closeup vision and distant vision. Answer in the order indicated. Separate your answers with a comma. Part B Find the powers of the correcting contact lenses needed to correct his closeup vision and distant vision. Answer in the order indicated. Separate your answers with a comma. Problem 25.24: Bifocals, I. A person can focus clearly only on objects between 37.5cmand 51.0cm from his eyes. Part A Find the focal lengths of the correcting contact lenses needed to correct his closeup vision and distant vision. Answer in the order indicated. Separate your answers with a comma. Part B Find the powers of the correcting contact lenses needed to correct his closeup vision and distant vision. Answer in the order indicated. Separate your answers with a comma. A person can focus clearly only on objects between 37.5cmand 51.0cm from his eyes. Part A Find the focal lengths of the correcting contact lenses needed to correct his closeup vision and distant vision. Answer in the order indicated. Separate your answers with a comma. Part B Find the powers of the correcting contact lenses needed to correct his closeup vision and distant vision. Answer in the order indicated. Separate your answers with a comma. Part A Find the focal lengths of the correcting contact lenses needed to correct his closeup vision and distant vision. Answer in the order indicated. Separate your answers with a comma. Part B Find the powers of the correcting contact lenses needed to correct his closeup vision and distant vision. Answer in the order indicated. Separate your answers with a comma. Part B Find the powers of the correcting contact lenses needed to correct his closeup vision and distant vision. Answer in the order indicated. Separate your answers with a comma.

Explanation / Answer

Part A)

To correct the near point, the normal eye has a near point of 25 cm, so

1/f = 1/p + 1/q

1/f = 1/37.5 + 1/-25

f = -75 cm

For the far point, we take objects from infinity

1/f = 1/infinity + 1/-51

f = -51 cm

So the answers are -75cm, -51cm

Part B

Take the inverse of the focal length, converted to meters

1/-.75 = -1.33 Diopters

1/-.51 = -1.96 Diopters

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