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| Derivation of Lens Formula (Concave Lens) |
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| Let AB represent an object placed at right angles to the principal axis at a distance greater than the focal length f of the convex lens. The image A1B1 is formed between O and F1 on the same side as the object is kept and the image is erect and virtual. |
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| OF1 = Focal length = f |
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| OA = Object distance = u |
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| OA1 = Image distance = v |
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| But from the ray diagram we see that OC = AB |
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| From equation (1) and equation (2), we get |
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| Dividing throughout by uvf |
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