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

AI Thread Summary
The focal length of a lens is influenced by its curvature, index of refraction, and thickness, with the curve and index being the most significant factors. The thin-lens approximation is commonly used, where thickness has minimal impact on focal length. An example illustrates that an imaginary air lens would not alter vision, while a glass lens would, emphasizing the importance of refractive index. The discussion highlights that while thickness can be a factor, it is often less critical in practical applications. Understanding these elements is essential for accurately determining a lens's focal length.
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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