Does the Refractive Index of a Lens Affect its Focal Length?

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Homework Help Overview

The discussion revolves around the factors that determine the focal length of a lens, specifically focusing on the role of the refractive index, lens curvature, and thickness. Participants are exploring the implications of these factors in the context of a test question.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the common understanding of focal length determination, questioning whether the refractive index should be included alongside lens curvature and thickness. There is also consideration of the thin-lens approximation and its relevance to the problem.

Discussion Status

The discussion is ongoing, with participants sharing their thoughts on the correct factors influencing focal length. Some express uncertainty about their reasoning and its implications for their test performance, while others provide insights into the relevance of the refractive index.

Contextual Notes

There is mention of a test context that may impose constraints on how participants are expected to respond regarding the factors affecting focal length. The discussion also touches on the typical treatment of lenses in high school physics, particularly the focus on thin lenses.

dranseth
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I just have one question regarding the focal length of a lens. I had a test today and there was a fill in the blank section regarding how the focal length of a lens is determined (there was two empty spaces.) Wouldn't there be three possible answers. The curve of the lens, the index of refraction, and the thickness of the lens? On the test I only stated the curve of the lens and the thickness..
 
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Usually it's safe (and common) to use a thin-lens approximation. I'd say the best two answers are index of refraction and curve of the lens, but thickness of the lens is technically correct also.
 
that's what I thought, I'll likely get that one wrong though due to my poor reasoning
 
In high school or thereabouts, only thin lenses are dealt with. The thickness does not matter much.

Suppose I hold an imaginary lens made of air in front of my eyes. Would I see anything different? But for a lens made of glass, I'll see differently. This logic is enough to answer that the ref index of the lens matters.
 

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