Problem 25.82 Part A Sam purchases +4.0-D eyeglasses which correct his faulty vi

Question

Problem 25.82 Part A Sam purchases +4.0-D eyeglasses which correct his faulty vision to put his near point at 25 cm. (Assume he wears the lenses 2.0 em from his eyes.) Calculate the focal length of Sam's glasses. Express your answer to two significant figures and include the appropriate units. f= | Value Units Submlt My Answers Give Up Part B Calculate Sam's near point without glasses. Express your answer to two significant figures and include the appropriate units. N-Value Units Submit My Answers Give Up Part C Pam, who has normal eyes with near point at 25 cm, puts on Sam's glasses. Calculate Pam's near point with Sam's glasses on. Express your answer to two significant figures and include the appropriate units. 1 Value Units Submit My Answers Give Up

Explanation / Answer

a) FOCAL LENGTH IS f = 1/P = 1/4 = 0.25 m = 25 cm

B) without glasses object distance is do = 25-2 = 23 cm

1/f = (1/do)+(1/di)

1/25 = (1/23)+(1/di)

di = -287.5 cm

near point is 289.5 cm

C) di = -25-2 = -27 cm

1/di + 1/di = 1/f

1/do = (1/f)-(1/di)

1/do = (1/25)-(-1/27)

do = 12.98 cm

distance of the object is 12.98+2 = 14.98 cm = 15 cm

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