# lenses

1. ### Finding optical power of corrective lenses?

The question is as follows: "A person with presbyopia has a near point of 40 cm. This person wears glasses to correct their vision such that they can comfortably read the screen of their mobile phone when it is held 25 cm from their eyes. If this person wears their glasses such that they sit...
2. ### Focal lenses

What are focal lenses?
3. ### Fibre-optics design question

Hello, I am trying to design something which needs to transfer as light as efficiently as possible from a 1W RGB LED, down 2 metres of a clear acrylic plastic rod/tube (used as an "optical fibre"), to a diffuser at the far end. The idea is is that total internal reflection will cause the light...
4. ### Lenses system

I am having some trouble understanding a question involving a lens system, which is as follows: A 20cm tall object is placed 80cm in front of a -6.75D lens. A second lens of power +3.00D is placed 7.5cm behind the first lens. The lens system is aligned so that the lenses are co-axial...
5. ### Converging + Diverging Lenses

Hi! I solved this problem, unfortunately I don't have the solution so I don't know if I'm correct. Can someone give it a try and let me know what you get? Thanks!
6. ### Lenses

Given a convex lens of focal length of (x+5) cm and a concave lens of focal length x cm. The 2 lenses are placed 30 cm apart coaxially i.e along the same axis with the convex lens on the left while the concave lens is on the right. A light bulb is placed to the left of the convex lens at a...
7. ### Two Converging Lenses

A compound microscope consists of two converging lenses. Lens 1, called the objective, is a distance 61.0 mm from lens 2, called the eyepiece. The objective is placed in between the object and the eyepiece. The objective has a focal length of 15.0 mm, and the eyepiece has a focal length of 25.5...
8. ### Light and lenses

In a convex lens if a object is 3 focal lengths away, it is possible to have a magnification of above 1?
9. ### Which of the glass lenses above...

http://i47.tinypic.com/20hahq9.jpg Which of the glass lenses above, when placed in air, will cause rays of light (parallel to the central axis) to diverge? 1. Z,B, and C 2. Z, P, B, and S 3. B and C 4. Z, C, and S 5. P and C 6. Z, B, and H 7. Z, H, and S 8. Z, P and H 9. P and H 10. Z, P, C, and S
10. ### combining lenses

I worked this problem and found some strange answers: 2 thin lenses separated by 10cm. First has a focal length of 20cm, the second has a focal length of 30cm. Here are my answers: Where H denotes the principle planes and O denotes the lenses. So here's the problem, recall that the lenses...
11. ### lenses and images

I've been trying to sort this problem out, but I've always had trouble with lenses... I know it's a relatively basic question, but I'm getting a weird answer. I'd really appreciate any help for this question. Thanks in advance! a)A lens is used to produce a real image of an object such that the...
12. ### "The Music" (angles, focal length, lenses, etc.) URGENT

The well known 17th Century Dutch painter Johannes Vermeer only painted 30 paintings during his life. However, they were created with incredible, almost photographic-like detail. The use of perspective was ahead of his time. Recently, many have come to wonder how Vermeer created such...