Have I Labeled 1/f=1/u+1/v Correctly?

  • Context: High School 
  • Thread starter Thread starter gracy
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Discussion Overview

The discussion revolves around the correct labeling of the thin lens formula, specifically the variables f, u, and v, in the context of optics. Participants explore the definitions and relationships between these variables, addressing potential misunderstandings related to focal length and measurement from the optical center.

Discussion Character

  • Homework-related
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants suggest that the original labeling of f, u, and v may be incorrect, particularly regarding the definition of f as the focal length rather than the distance from the lens to the image.
  • One participant acknowledges confusion about the focal point and focal length, indicating that the distances should be measured from the optical center.
  • Another participant recommends consulting a school physics textbook for reliable information and suggests that educational quality may vary by region.

Areas of Agreement / Disagreement

Participants express differing views on the correct labeling of the variables, with some agreeing on the definitions while others remain uncertain about their understanding. The discussion does not reach a consensus on the correct labeling.

Contextual Notes

Participants note limitations in their understanding of the focal point and focal length, as well as the importance of measuring distances from the optical center, but do not resolve these issues.

Who May Find This Useful

This discussion may be useful for students studying optics, particularly those grappling with the thin lens formula and its components.

gracy
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Have I labeled correctly?
have i labeled it correctly.png
 
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This looks like it should be posted in the schoolwork forums, gracy. And are you familiar with the thin lens formula? That is basically what you are asking about. Check it out on wikipedia for more info.
 
gracy said:
Have I labeled correctly?
Almost. u and v are correct, but not f. f is the focal length of the lens, not the distance from lens to image. (That's what v is.) Look it up!
 
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Doc Al said:
f is the focal length of the lens, not the distance from lens to image. (That's what v is.)
I got you point.I think the image below greatly explains all the three f,v,u.
diagram10.gif

I was doing following mistakes.
1-I was not considering focal point . If the light rays converge (as in a converging lens), then they will converge to a point. This point is known as the focal point of the converging lens. If the light rays diverge (as in a diverging lens), then the diverging rays can be traced backwards until they intersect at a point. This intersection point is known as the focal point of a diverging lens.
2-I was confused about focal length.Focal length is distance between optical center and focal point.
3-All the distance should be measured from optical center.So ,in the previously attached image i.e
65921-bd501138b1af5041ab392f82387e353b.jpg

u and v was not correct in the sense that the distance was not measured from optical center.I think that's what you meant by
Doc Al said:
Almost u and v are correct
 
Last edited:
@gracy
Do you have a good old fashioned School Physics Text Book? Many of the questions you have been asking (on this and other topics) are dealt with in books and you can usually rely on them to get things right.
It may depend upon which part of the world you are getting your Science education and I know there are some ridiculously elementary Science courses in some places. If your course is badly lacking, then you really should invest in a decent book. These days, the Internet can get any book to anybody, anywhere. It may be your best way forward.
 
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