Contact Lenses Optics Problem (Two-Parts)

[DylanXO]

I believe I have answered the first question correctly (although I am not certain of this). And I'm struggling with grasping how to approach the second part of the question. Any guidance or recommedations on reading material would be greatly appreciated.

Homework Statement

1. Contact lenses are placed right on the eyeball, so the distance from the eye to the object is the same as the distance from the lens to that object. A certain person can see distant objects well, but the near point is 45.0 cm from the eye instead of 25.0 cm.
   • Is this person near sighted or far sighted?
   • What type of lens is necessary to correct his vision?
   • If the correcting lenses will be contact lenses, what focal length is needed?
   • What is the power in diopters?
2. Repeat the previous question for ordinary glasses where the lenses are 2.0 cm in front of the eyeball.

• Is this person near sighted or far sighted?
• What type of lens is necessary to correct his vision?
• If the correcting lenses will be contact lenses, what focal length is needed?
• What is the power in diopters?

Homework Equations

f=ss'/(s+s')
Diopters = 1/f

The Attempt at a Solution

Part 1[/B]
A) Is this person near sighted or far sighted? Farsighted
B) What type of lens is necessary to correct his vision? Converging Lens
C) f=ss'/(s+s')= (25)(-45)/(25-45)= +56.26cm
D) Diopters = 1/f = 1/(0.5625) = 1.78 Diopters

Part 2
A) Is this person near sighted or far sighted? Farsighted? (This is just a hunch)
B) What type of lens is necessary to correct his vision? Converging Lens? (This is also just a hunch)
C)
D)

 

[BvU]

I agree with your hunches: A because it is the same person and B because the correction needed is in the same 'direction'.
C0 is reproduced incorrectly, I suppose you want

• If the correcting lenses will be glasses lenses, what focal length is needed?

and you'll need a new equation that somehow involves these 2 cm between glass lens and eye lens...

Perhaps making a sketch can help ?

 

[DylanXO]

I agree with your hunches: A because it is the same person and B because the correction needed is in the same 'direction'.
C0 is reproduced incorrectly, I suppose you want

• If the correcting lenses will be glasses lenses, what focal length is needed?

and you'll need a new equation that somehow involves these 2 cm between glass lens and eye lens...

Perhaps making a sketch can help ?

Thanks, I will try making a sketch now and see where that gets me!