art A C Exercise 25.18 If the near points in the right and left eyes are 33.0 cm

Question

art A C Exercise 25.18 If the near points in the right and left eyes are 33.0 cm and 47.0 cm , respectively, and the far point is 240 cm for both eyes, what are the powers of the lens prescribed for the right eye? (Assume that the glasses are worn 3.00 cm from the eyes.) Bifocal glasses are used to correct both nearsightedness and farsightedness at the same time. (Figure 1) Enter your answers in ascending order separated by commas Figure 1 of 1 Submit My Answers Give Up Part B What are the powers of the lens prescribed for the left eye? Nearsightedness correction Enter your answers in ascending order separated by commas Farsightedness correction

Explanation / Answer

G = glasses distance to eye = 3cm
Fp = far point (without glasses he can see farther than this point)
right Fp = 240cm

Di = Fp - G = 240 - 3 = 237cm
Do = infinity
1/F = 1/Do - 1/Di
1/F = 0 - 1/237
F = - 237cm
P = 100/F = - 0.42 diop <=== right eye

P = - 0.42 diop <========== left eye

farsightedness

G = glasses distance to eye = 3cm
Np = near point (without glasses he cannot see closer than this point)
Np = 33cm --- right eye
Np = 47cm --- left eye

Di = Np - G = 33 - 3 = 30cm --- right eye
Di = Np - G = 47 - 3 = 44cm --- left eye

assumed he wants to read a book Do = 22cm for both eyes

1/F = 1/Do - 1/Di
F = (Do * Di) / (Di - Do)

F = 82.5 cm --- right eye
F = 44.00cmcm --- left eye

P = 100 / F = 100 / 82.5 = 1.21 diop <=== right eye
P = 100 / F = 100 / 44.00 = 2.27 diop <=== left eye

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