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: 

`1/v-1/u=1/f`
Now, the mirror formula is given by:

`1/v+1/u=1/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.