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Lens Formula
Lens Formula
Lens formula is common for both, convex and concave, the lenses. It gives the relationship between image distance, object distance and focal length. To solve the numerical, use of sign convention is important.
In formula
u = object distance
v = image distance
f= focal length.
Sign conventions for lens
All distances are measured from the optical centre of the lens.
Keep the object towards the left side of the lens.
The distance measured to the left of the lens/ optical centre is negative.
The distance measured to the right of lens/ optical centre is negative.
The distance measured above the principal axis of the lens is positive.
The distance measured below the principal axis of the lens is negative.
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