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## Homework Statement

a)A person has a near point of .6m and far point of 2m . What power of glasses would be needed for the person to see infinitely far away. Assume that glasses are 2cm from the person's eyes. If the person used those glasses, what would his new near point be?

b) What power of glasses would be needed to bring the person's near point to .25m. If the person used those glasses, what would their new far point be?

## Homework Equations

1/f = 1/o + 1/i

P=1/f

## The Attempt at a Solution

This is what I have so far.

I know that

1/f = 1/o + 1/i

I want an image at infinity so 1/f = 1/o

The object is 2m from the eyes so it is 1.98 m from the glasses. The direction of the light is toward the glasses while the image is in the opposite direction. so o is negative.

1/-1.98 = -.505

And this is the correct answer according to the answer key.

I have problem solving for the new near point though.

1/f = 1/o + 1/i

-.505 = 1/o + 1/i

I want to create a new image for a distance of .6 m from the eyes or .58 from the glasses

-.505 = 1/.58 + 1/-i

-1/1.98 - 1/.58 = -1/i

I get i = .44 meters

but the correct answer is .82 meters. What did i do wrong?

I am having a similar problem for part b so I think I can get it if I find out what I did wrong here in part a.

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