Optics - Defining front and back of lens

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SUMMARY

The discussion centers on the definitions of the front and back of a lens in optics, particularly in the context of a divergent lens and a concave mirror. The key takeaway is that the front of the lens is defined as the face that receives incoming rays, while the back is where the rays exit after refraction. The object is always considered to be in front of the lens when it is positioned on the same side as the incoming light, regardless of the image formation by the concave mirror. Understanding these sign conventions is crucial for accurately determining image locations.

PREREQUISITES
  • Basic knowledge of optics, specifically lens and mirror behavior.
  • Familiarity with divergent lenses and concave mirrors.
  • Understanding of sign conventions in optics.
  • Ability to measure distances from the center of a lens.
NEXT STEPS
  • Study the principles of ray diagrams for divergent lenses.
  • Learn about the sign conventions used in optics, particularly for lenses and mirrors.
  • Explore the concept of image formation by concave mirrors.
  • Investigate the mathematical relationships governing lens and mirror systems.
USEFUL FOR

Students and professionals in physics, particularly those focusing on optics, as well as educators seeking to clarify lens and mirror concepts for learners.

MichaelT
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Working on some optics problems and I am confused about the front and back of the lens. The sign conventions are key to finding the correct image location. Now, is the front always where the object is located?

The problem I am working on involves a divergent lens and a concave mirror. The object is in front of the lens. An image forms in front of the lens. Then the concave mirror forms an image between the lens and the mirror, which would be on the opposite side of the lens.

Would the object now be considered as being in back of the lens, or would it be the front? The other side of the lens was previously the front. Does this change, or is one side considered the front for the whole problem?

Thanks!
 
Physics news on Phys.org
Instead of saying front and back of lens, you can say , the face which receives the ray and the face which refract the ray. Measure the distances from the center of the lens.
 

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