To obtain a magnification of 2.5, how far should an object be placed from the pole of a thin converging lens of focal length 10.20m?

To obtain a magnification of 2.5, how far should an object be placed from the pole of a thin converging lens of focal length 10.20m?

Answer Details

v = 2.5u

F = $\frac{uv}{u+v}$

0.2 = $\frac{u\times 2.5u}{u+2.5u}$

u = 0.28m