Lens maker's equation used correctly?

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SUMMARY

The discussion centers on the application of the lens maker's equation to a thick double convex lens with specific parameters: object distance of 60 cm, radii of curvature of 20 cm and 30 cm, thickness of 2 cm, and an index of refraction of 1.5. The correct image position calculated using the lens maker's equation is 39.9 cm, while an incorrect calculation yielded 40 cm. Participants emphasized the necessity of incorporating the lens thickness into the calculations, as neglecting it can lead to inaccuracies in the image position.

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  • Knowledge of refraction and index of refraction concepts
  • Basic algebra for manipulating equations
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Homework Statement



An object is placed 60 cm from a thick double convex lens, with faces of radii of curvature 20 cm and 30 cm, with thickness of 2 cm, and index of refraction is 1.5. Find the position of the image. Ans: ( 39.9 cm)

Homework Equations



lens maker's equation, na/object + na/image = (nb - na)(1/R1 - 1/R2)

The Attempt at a Solution



I used this equation and got 40 cm, as opposed to 39.9. I figured it couldn't be a rounding error considering the numbers given. Am I supposed to use the 2 cm thickness somehow?
 
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When I calculated the answer, it came out to be 40.9 cm. Strange! I used the lensmaker equation given in Wikipedia. These were my results : f= 900/37 cm, u=-60 cm (given) So, using lens formula v = 40.9cm. And yes you need to use the thickness. See the lensmaker's equation in Wikipedia!
 
@Danny :the equation which you are using seems to be derived from thin lens equation where you neglect thickness as it's too small compared to Radii of curvature.
 

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