Geometric Optics and Lens Power

[CCR5]

Homework Statement

A farsighted boy has a near point at 2.3 m and requires eyeglasses to correct his vision.

Corrective lenses are available in increments in power of 0.25 diopters. The eyeglasses

should have lenses of the lowest power for which the near point is no further than 25

cm. The correct choice of lens power for eyeglasses, in diopters, is:

Homework Equations

1/s + 1/s' = 1/f
1/f = P

The Attempt at a Solution

I keep getting a value of 3.57 diopters, however, the correct answer is 3.75.

 

[kuruman]

Corrective lenses are available in increments in power of 0.25 diopters.

3.57 diopters does not exist as a choice.

 

[CCR5]

3.57 diopters does not exist as a choice.

Wonderful... Can you shed some light on the increment and its relation to the correct answer of 3.75?

 

[fresh_42]

Can you shed some light on the increment ...

You already answered this by yourself!

Corrective lenses are available in increments in power of 0.25 diopters.

... and its relation to the correct answer of 3.75

Ergo: you have to chose between 3.5 and 3.75. Now you have to calculate which distance at diopters of 3.5 or 3.75 fulfills the requirement "near point no further than ..."

 

[CCR5]

You already answered this by yourself!Ergo: you have to chose between 3.5 and 3.75. Now you have to calculate which distance at diopters of 3.5 or 3.75 fulfills the requirement "near point no further than ..."

Errm. So based off the given answers, which ever is closest to to my value an estimated value of 0.25 increment? Gotcha! Thank you for your response.