# Contact Lenses Optics Problem (Two-Parts)

• DylanXO
In summary, the conversation discusses a person who can see distant objects well but has difficulty with near objects, and the necessary corrective lenses for this person. For contact lenses, a converging lens with a focal length of +56.26 cm and a power of 1.78 diopters is needed. For ordinary glasses, a new equation taking into account the 2 cm distance between the glass lens and eye lens is needed to determine the necessary focal length.
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?

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)

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
BvU said:
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!

## Question 1: What is the difference between soft and rigid gas permeable (RGP) contact lenses?

Soft contact lenses are made of a flexible, water-containing plastic material that conforms to the shape of the eye. RGP lenses are made of a rigid, oxygen-permeable material that allows for better oxygen flow to the eye. Soft lenses are typically more comfortable to wear, while RGP lenses provide sharper vision and are more durable.

## Question 2: How do contact lenses correct vision problems?

Contact lenses work by altering the way light rays enter the eye, correcting vision problems such as nearsightedness, farsightedness, and astigmatism. They do this by refracting light in a way that compensates for the eye's natural shape, allowing for clearer vision.

## Question 3: Can contact lenses correct presbyopia?

Yes, there are contact lenses designed specifically for correcting presbyopia, a condition that occurs with age and makes it difficult to see objects up close. These lenses are called multifocal or bifocal contact lenses and have different prescription powers in different areas of the lens to allow for clear vision at all distances.

## Question 4: How often should contact lenses be replaced?

The frequency of contact lens replacement depends on the type of lens. Daily disposable lenses should be discarded after one day of use, while monthly or bi-weekly lenses should be replaced according to the recommended schedule. It is important to follow the replacement schedule to maintain eye health and prevent infections.

## Question 5: Are there any risks associated with wearing contact lenses?

Wearing contact lenses does carry some risks, such as eye infections, dry eyes, and corneal abrasions. However, these risks can be minimized by following proper hygiene and care instructions, replacing lenses as recommended, and visiting an eye doctor regularly for check-ups and adjustments. It is also important to avoid sleeping in contact lenses and to remove them immediately if any discomfort or redness occurs.

• Introductory Physics Homework Help
Replies
1
Views
669
• Introductory Physics Homework Help
Replies
4
Views
2K
• Introductory Physics Homework Help
Replies
1
Views
4K
• Introductory Physics Homework Help
Replies
1
Views
987
• Introductory Physics Homework Help
Replies
4
Views
771
• Introductory Physics Homework Help
Replies
2
Views
1K
• Introductory Physics Homework Help
Replies
2
Views
1K
• Introductory Physics Homework Help
Replies
1
Views
1K
• Introductory Physics Homework Help
Replies
3
Views
877
• Introductory Physics Homework Help
Replies
3
Views
2K