Why do light rays continue to bend towards the center after exiting a convex lens?

In summary, light rays entering a convex lens bend towards the center due to refraction. When exiting the lens, they continue to bend towards the center due to the change in direction of the Normal at the exit point. This results in a second bending towards the center, as seen in a biconvex lens, rather than a straightening of the ray.
  • #1
sk381
19
0
Hi,

I know that when entering a convex lens, light rays bend towards the center due to refraction. But why do they keep bending towards the center once they exit the lens? Should'nt they now bend away from the lens because they are going from a denser to a rarer medium?

Thanks

SK
 
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  • #2
Yes, the light rays bend away from the Normal to the surface when exiting the lens. But the ray still has changed direction due to the variation in optical path length through the lens.
 
  • #3
I am still not clear..
Can you explain more in detail..?

Thanks
 
  • #4
Do you understand the meaning of Normal in this usage?
 
  • #5
yes.. I think you mean the line perpendicular to the surface of the convex and parallel to the direction that the ray is traveling in..right/
 
  • #6
It is because the curve switches in a biconvex lens.

If the lense were like this (( you would get a straightening of the ray.

But if it is like this () you get a second bending toward the center.

Njorl
 
  • #7
As Norjl said, because the Normal is pointing in a different direction at the exit point.
 

1. What is a convex lens?

A convex lens is a type of lens that is thicker in the middle and thinner at the edges. It is also known as a converging lens, as it causes light rays to converge or come together at a point.

2. How does a convex lens work?

A convex lens works by refracting or bending light rays as they pass through it. The thicker middle part of the lens causes the light rays to bend towards the center, converging at a focal point. This allows the lens to magnify objects and form images.

3. What are the applications of convex lenses?

Convex lenses have various applications in everyday life, such as in eyeglasses, magnifying glasses, telescopes, and cameras. They are also used in scientific instruments like microscopes and projectors.

4. How is the focal length of a convex lens determined?

The focal length of a convex lens is the distance between the lens and its focal point. It can be determined by using the lens equation: 1/f = 1/v + 1/u, where f is the focal length, v is the distance of the image from the lens, and u is the distance of the object from the lens.

5. Can convex lenses form both real and virtual images?

Yes, convex lenses can form both real and virtual images depending on the position of the object relative to the lens. When the object is placed beyond the focal point, a real image is formed. When the object is placed between the lens and the focal point, a virtual image is formed.

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