Physics - Geometrical Optics Question with Solution | TestHub

From the lens formula: $\frac{1}{f}=\frac{1}{v}-\frac{1}{u}$ we have, $\frac{1}{f}=\frac{1}{10}-\frac{1}{-10}$ or $f=+5$ Further, $\Delta u=0.1$ and $\Delta v=0.1$ (from the graph) Now, differentiating the lens formula we have, $$\frac{\Delta f}{f^2}=\frac{\Delta v}{v^2}+\frac{\Delta u}{u^2}\text{ or }\Delta f=\left(\frac{\Delta v}{v^2}+\frac{\Delta u}{u^2}\right)f^2$$ Substituting the values we have, $$\Delta f=\left(\frac{0.1}{10^2}+\frac{0.1}{10^2}\right)(5{)}^2\Rightarrow f\pm \Delta f=5\pm 0.05$$