How Do You Calculate Object Distance in Lens Equations?

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Homework Help Overview

The problem involves calculating the object distance for a converging lens given the focal length and the image distance. The context is within the subject area of optics, specifically lens equations.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the application of the lens formula and question the interpretation of the image distance in relation to the focal length. There are attempts to solve for the object distance using different setups of the lens equation.

Discussion Status

Some participants have provided insights into their reasoning and calculations, while others have pointed out potential misunderstandings regarding the setup of the problem. There is a recognition of errors in calculations, but no consensus has been reached on the correct approach.

Contextual Notes

There is confusion regarding the interpretation of the image distance being "behind" the lens and how it relates to the focal length. Participants are also navigating the constraints of the problem as presented in the homework assignment.

sp1974
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The homework problem is "A sharp image is located 68.0 mm behind a 56.0 mm focal length converging lens. Calculate the object distance in millimeters"



1/f = 1/di + 1/do



I tried solving based on having focal (f) and distance of image (di) so 1/56 mm = 1/(68 mm + 56 mm) + 1/do
I solved for do coming up with 102.04 mm and the computer doesn't accept
 
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Why is di=68+56?
 
I figured because the focal point was 56 and it says 68 behind it so I thought it would be f distance + the 68
 
It states it is behind a 56mm focal length lens. Not 68mm behind the focal length of a 56mm focal length lens.
 
I also did it as 1/56 = 1/68 + 1/do and the computer didnt accept that on as well
 
ok I figured this one out. I had my numbers flip flopped my numbers when subtracting
 

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