Write the relation between linear magnification (m), u & f.

Explanation

Linear magnification in terms of u and f
We know that, for a lens,`-1/u+1/v=1/f`
Multiplying both sides by u, we have
`-u1/u+u1/v=u1/f" "implies" "-I+u/v=u/f" "implies" "u/v=u/f+1`
`implies" "u/v=(u+f)/f" "implies" "v/u=f/(u+f)`
But`" "v/u=m" ":." "m=f/(u+f)`.