Optics, plz check my answers, and if they r not right, plz show me the right ones, thx?

Question

1).Use the equation 1/o + 1/i = 1/f to solve the problem. Object distance is o, image distance is i, and focal length is f. When you focus on a newspaper page, the lens in your eye forms a real image of the paper on the retina in the back of your eye. The light-sensitive retina then translates the patterns of light and dark areas to your brain, which in turn interprets them as words. If your newspaper is 29.0 cm from your eye, and the focal length of your eye is 2.4 cm, what is the diameter of your eye from front to back? (The diameter of your eye is the image distance.)

I did 1/29+1/i=1/2.4
1/29-1/2.4=1/i now would i just solve and get the right answer? to be the result of 1/2.4-1/29?

2).Consider a simple magnifying glass under water. Will it magnify more or less than in the air?
more
less
not enough information to decide

i said more, because light travels faster in water thus enabling it to be magnified more?

Answer 1

You got carried away -reorder the eqn to isolate i:
1/f-1/o =1/i; so i = fo/(o-f) = (29*2.4)/ (29-2.4) =2.6 cm
As to the second question, what do you know about the size of objects as they appear underwater?

Answer 2

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Answer 3

>I did 1/29+1/i=1/2.4
1/29-1/2.4=1/i now would i just solve and get the right answer? to be the result of 1/2.4-1/29?<

Now, take the reciprocal of that result.

The glass would magnify less under water, since the amount is dependant on the difference of speed of light in the media- air to glass versus water to glass.