Question

Write the formula for a lens connecting image distance (v), object distance (u) and the focal length (f). How does the lens formula differ from the mirror formula?

Answer 1

Lens formula is:
$\frac{1}{\mathrm{v}}-\frac{1}{\mathrm{u}}=\frac{1}{\mathrm{f}}$
Now, the mirror formula is given by:
$\frac{1}{\mathrm{v}}+\frac{1}{\mathrm{u}}=\frac{1}{\mathrm{f}}$
In both the formulas,
u = Object distance
v = Image distance
f = Focal length
In mirror formula, positive sign is present between the reciprocals of image distance and object distance .
In lens formula, negative sign is present between the reciprocals of image distance and object distance.