Optical Lens Formula

 

Convex Lens (Real Image)

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Consider an object AB held perpendicular to the principal axis at distance beyond the focal length of the lens. A real, inverted and enlarged image is formed as shown.

But CD=AB

It follows

BC = -u

B^lC = +v using sign convention

CF = +f

FB^l = CB^l - CF = v - f

vf = -uv + ufuv = uf - vf

Dividing throughout by uvf

Note:

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(1) The above formula is applicable for a convex lens when a virtual image is formed. For this the following ray diagram is to be considered.

2) For concave lens, the ray diagram would be

Linear Magnification Produced by a Lens

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Convex Lens

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Real Image

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Virtual Image

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Concave Lens

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