Understanding Converging Lenses: Question on Image Size

In summary, the given question involves finding the solution for a lens problem represented by blue rays. The object and image are the same size and parallel rays from the object converge at a point on the focal plane. The image size is the same as the object size due to symmetry around the optical axis. The magnification formula is also mentioned.
  • #1
dioprem
11
0

Homework Statement



This is the given question. The blue rays represent the solution.
http://img16.imageshack.us/img16/7237/lenstq.jpg



Homework Equations


None.


The Attempt at a Solution



The blue rays are essentially my solutions, but only up to the point where the rays are reflected off the mirror. The rays after hitting the lens after that are from my teacher. Once they hit the lens, I know the 2 rays need to converge at a point along the focal plane, since the rays are parallel. What I want to know is why is the image the same size as the object?
 
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  • #2
Try drawing rays from other points on the needle such a point Y.
 
  • #3
CWatters is right. Rays from X and Y are parallel.
 
  • #4
@CWatters The problem is the solution requires me to only draw to rays from point X. So I cannot draw addition rays from point X or any other rays from any other point of the needle. Only 2 rays from X are allowed. So I don't understand why the image is the same size as the object.
 
  • #5
Consider a third ray from X which hits M right in the middle (you don't have to draw it). It is symmetric around the optical axis, and it has to hit the same point as the other two rays. Y is projected on itself. Therefore, the image of (XY) has the same size as (XY).
 
  • #6
magnification = - image distance/object distance
 
  • #7
Thank you mfb and Basic_Physics. Answered my question!
 

FAQ: Understanding Converging Lenses: Question on Image Size

What is a converging lens?

A converging lens is a type of lens that is thicker in the middle and thinner at the edges. It causes parallel rays of light to focus at a single point, known as the focal point.

How does a converging lens work?

A converging lens works by refracting (bending) light as it passes through the lens. The shape of the lens causes the light rays to converge, or come together, at the focal point on the other side of the lens.

What is the difference between a converging lens and a diverging lens?

The main difference between a converging lens and a diverging lens is the way they bend light. A converging lens causes light rays to converge at a focal point, while a diverging lens causes light rays to spread out.

What are some real-life applications of converging lenses?

Converging lenses are commonly used in eyeglasses, cameras, telescopes, and microscopes. They are also used in laser pointers and projectors to focus light into a narrow beam.

How do you calculate the focal length of a converging lens?

The focal length of a converging lens can be calculated using the formula: f = 1/(n-1) * (1/R1 - 1/R2), where f is the focal length, n is the refractive index of the lens material, and R1 and R2 are the radii of curvature of the two surfaces of the lens.

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