Does Light Focus When Passing Through Converging and Diverging Lenses?

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SUMMARY

The discussion centers on the optical behavior of a converging lens and a diverging lens separated by a distance greater than the focal length. The converging lens focuses parallel light rays to a focal point, while the diverging lens refracts the light, creating a virtual image. The key conclusion is that the converging lens successfully focuses the light, but the diverging lens does not contribute to this focusing effect. The virtual image formed by the diverging lens does not equate to light being focused in the traditional sense.

PREREQUISITES
  • Understanding of lens types: converging and diverging lenses
  • Familiarity with focal length concepts
  • Knowledge of the lens formula: 1/f = 1/do + 1/di
  • Basic principles of light refraction
NEXT STEPS
  • Study the principles of ray diagrams for converging and diverging lenses
  • Explore the concept of virtual images in optics
  • Learn about the effects of lens separation on image formation
  • Investigate the applications of lens systems in optical devices
USEFUL FOR

Students studying optics, physics educators, and anyone interested in understanding the behavior of light through lens systems.

gingerelle
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Homework Statement



A converging lens has a focal length f, and a diverging
lens has a focal length –f, which has the same magnitude
as the converging lens. They are separated by a distance
D which is greater than f, as shown. Parallel light enters
from the left. Will the light be brought to a focus, and if
so where?

(basically there are two lenses. The converging lens is on the left of the diverging lens. The two are separated by some distance d. There are parallel horizontal rays traveling to the converging lens.)

Homework Equations



1/f = 1/do + 1/di ?

The Attempt at a Solution



I'm not really sure how to approach this question, but I would like to confirm some of my thoughts first (to avoid finding out I was wrong to think a certain way later). The parallel horizontal rays that hit the converging lens should go through the lens, pass through the focal point...and all be going from the focal point and out in a diverging manner.

The light that's passed through the converging lens will then pass through the diverging lens, being refracted. This will form a virtual image in between the focal point and the diverging lens.

However, the formation of this virtual image...is that considered as light being focused?

Anyway...that's basically my thinking. Is this correct or am I missing something important?
 
Last edited:
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Your logic looks impeccable to me.
The converging lens brings the light to a focus;
The diverging lens doesn't.
The question looks so easy, am I missing something?
 

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