Why do different types of lenses have different effects on image size and focus?

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SUMMARY

Different types of lenses, specifically BiConvex lenses, exhibit distinct behaviors regarding image size and focus due to their physical properties. Increasing the lens radius in BiConvex lenses brings the image closer and reduces its size, while the human eye's ciliary muscles contract to fatten the lens, resulting in a larger image for nearby objects. The refractive index also plays a crucial role, as a higher refractive index causes the image to focus closer to the lens. These observations highlight the differences in lens functionality between optical devices and biological systems.

PREREQUISITES
  • Understanding of BiConvex lens properties
  • Knowledge of optical physics, specifically image formation
  • Familiarity with the human eye's accommodation mechanism
  • Basic principles of refraction and refractive index
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  • Explore the principles of lens design and optical aberrations
  • Study the effects of varying refractive indices on image formation
  • Investigate the mechanics of the human eye's ciliary muscles and their impact on vision
  • Learn about different types of lenses and their applications in optical devices
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Optics students, optical engineers, educators in physics, and anyone interested in the mechanics of lenses and vision.

Hereformore
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So for BiConvex Lenses, increasing the lens radius (by making the lens fatter) brings the image and focus closer to the lens, thus making it smaller given constant object position. As demonstrated in this demo
http://micro.magnet.fsu.edu/primer/java/lenses/lensvariations/index.htmlYet for the eye, when we want to focus on closer objects, the ciliary muscles contract to fatten the lens and that makes the image larger, not smaller? As demonstrated in this demo: http://micro.magnet.fsu.edu/primer/java/humanvision/accommodation/index.html

Why are they conflicting? Are they different lenses?

And while we're on the subject, increasing the refractive index of a lens definitely causes the image to focus closer to the lens right?
 
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I don't know what you are seeing, but when I increase the lens radius in the first link, the focus moves further away from the lens. This would make it consistent with the second demo.
 
TheDemx27 said:
I don't know what you are seeing, but when I increase the lens radius in the first link, the focus moves further away from the lens. This would make it consistent with the second demo.
Sorry i wasnt clear! When i said radiuss i meant the radiuss that is always double the focal length, not the radius of the glass lens itself.
 

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