How to find the focal length of a lens?

I need some help with finding the focal length of a double convex lens. If possible could you tell me the formula for finding it. Many thanks…

You’ll need to know a few parameters for the lens. Specifically the radii of curvature of the two surfaces and their separation.

Use the formula found here http://en.wikipedia.org/wiki/Lens_(optics)#Lensmaker.27s_equation

If d is small compared to the radii of curvature then the last term in the equation can be ignored.

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One Response to How to find the focal length of a lens?

  1. Euan R says:

    You’ll need to know a few parameters for the lens. Specifically the radii of curvature of the two surfaces and their separation.

    Use the formula found here http://en.wikipedia.org/wiki/Lens_(optics)#Lensmaker.27s_equation

    If d is small compared to the radii of curvature then the last term in the equation can be ignored.
    References :