Solving Lens Problem: Eyeglasses w/ 2 Converging Lenses

  • Thread starter Alt+F4
  • Start date
In summary: Distance = f/(x1+x2)SO at x1 = 0.397 m and x2 = 1 m, the distance between the lenses is 0.8 m. So the size of the image is 0.2 m on the right side and 0.25 m on the left side.(b) What is the height of the image formed by Lens 1?The height of the image formed by Lens 1 is 3.9 cm.
  • #1
Alt+F4
306
0
Lenses Problem

In the figure are shown two converging lenses with x2 = 1 m. The lens on the left (Lens 1) has a focal length of 0.25 m while the one on the right (Lens 2) has a focal length of 0.2 m. An object 3.9 cm high is located x1 = 0.397 m to the left of Lens 1.


http://img153.imageshack.us/img153/123/showmeal3.gif [Broken]


--------------------------------------------------------------------------------
(a) Consider the image of the object formed by Lens 1. Give its distance as measured from Lens 1 and the image height.
Distance = m


SO i was trying to use the thins line equation which is 1/ o + 1/f = 1/I but i don't know what numbers to plug in
 
Last edited by a moderator:
Physics news on Phys.org
  • #2
Drawing the ray diagram for this system of lenses would be very useful. The first lens will form an image. You can use the lens equation to help you locate it. Then think about what the second lense does to the light coming from (or going toward) the image of the first lens.
 
Last edited:
  • #3
i have no idea, can i get more help
 
  • #4
Alt+F4 said:
i have no idea, can i get more help
Do the problem as if the lens on the right were not there to locate the image formed by the first lens. It will be between the two lenses. When you know the position of the image, you can also find the height of the image. Use your thin lens formulas.

As far as the second lens knows, the light coming to it from the image of the first lens is light from some object. So treat the image from the first lens as an object for the second lens and do a new problem to find the image formed by the second lens.

Check the lens equation you originally posted. You have some terms mixed up.
 
Last edited:
  • #5
Here is a diagram that might help you through this. For your part a) you only need the first lens. I assume later parts talk about the second lens. Note that the size of the original image is much larger than scale, which is why the lines are so far off axis. The blue rays are actual paths light could take. The red line through the second lens is added to help locate the final image.

All you need to do is apply the lens equation once to find the image between the lenses, and then a second time to find the final image. The image sizes are determined by the ratio of image distance to object distance.
 

Attachments

  • TwoLens.jpg
    TwoLens.jpg
    13.6 KB · Views: 467
Last edited:

1. How do I determine the focal length of converging lenses for my eyeglasses?

The focal length of a converging lens can be determined by using the lens formula, which states that the focal length (f) is equal to the product of the refractive index of the lens (n) and the radius of curvature (R) divided by the difference between the refractive index of the lens and the refractive index of the surrounding medium (n-n'). This can also be calculated by using a lensometer, which measures the distance between the lens and the focal point.

2. What is the best way to position the lenses in my eyeglasses for optimal vision correction?

The lenses in eyeglasses should be positioned so that they are centered directly in front of the pupils of the eyes. This will ensure that the light entering the eyes is properly refracted and focused, providing the best possible vision correction.

3. Can I use two different types of converging lenses in my eyeglasses?

Yes, it is possible to use two different types of converging lenses in eyeglasses. This is often done to correct for different types of vision problems, such as nearsightedness and farsightedness. However, it is important to consult with an optometrist to ensure that the lenses are properly aligned and that the vision correction is effective.

4. How do I know if my eyeglasses have the correct power of lenses?

The power of lenses in eyeglasses is measured in units called diopters. The correct power of lenses can be determined through a comprehensive eye exam by an optometrist. They will take into account the individual's vision prescription, the distance between the lenses and the eyes, and the desired visual acuity for the individual's lifestyle.

5. Is there a limit to the strength of lenses that can be used in eyeglasses?

There is no specific limit to the strength of lenses that can be used in eyeglasses. However, very strong lenses may cause distortion or discomfort for the wearer and may not provide optimal vision correction. In these cases, other methods such as contact lenses or corrective surgery may be recommended by an optometrist.

Similar threads

  • Introductory Physics Homework Help
Replies
1
Views
916
  • Introductory Physics Homework Help
Replies
3
Views
1K
  • Introductory Physics Homework Help
Replies
1
Views
1K
  • Introductory Physics Homework Help
Replies
2
Views
2K
  • Introductory Physics Homework Help
Replies
3
Views
1K
  • Introductory Physics Homework Help
Replies
3
Views
1K
  • Introductory Physics Homework Help
Replies
7
Views
1K
  • Introductory Physics Homework Help
Replies
10
Views
1K
  • Introductory Physics Homework Help
Replies
5
Views
1K
Replies
10
Views
1K
Back
Top